Bone metastatic prostate cancer does not completely respond to androgen-targeted therapy and generally evolves into lethal castration resistant prostate cancer (CRPC). Expression of AR-V7- a constitutively active, ligand independent splice variant of AR is one of the critical resistant mechanisms regulating metastatic CRPC. TNC is an extracellular matrix glycoprotein, crucial for prostate cancer progression, and associated with prostate cancer bone metastases. In this study, we investigated the mechanisms that regulate AR-V7 expression in prostate cancer cells interacting with osteogenic microenvironment including TNC.Prostate cancer/preosteoblast heterotypical organoids were evaluated via immunofluorescence imaging and gene expression analysis using RT-qPCR to assess cellular compartmentalization, TNC localization, and to investigate regulation of AR-V7 in prostate cancer cells by preosteoblasts and hormone or antiandrogen action. Prostate cancer cells cultured on TNC were assessed using RT-qPCR, Western blotting, cycloheximide chase assay, and immunofluorescence imaging to evaluate (1) regulation of AR-V7, and (2) signaling pathways activated by TNC. Identified signaling pathway induced by TNC was targeted using siRNA and a small molecular inhibitor to investigate the role of TNC-induced signaling activation in regulation of AR-V7. Both AR-V7- and TNC-induced signaling effectors were targeted using siRNA, and TNC expression assessed to evaluate potential feedback regulation.Utilizing heterotypical organoids, we show that TNC is an integral component of prostate cancer interaction with preosteoblasts. Interaction with preosteoblasts upregulated both TNC and AR-V7 expression in prostate cancer cells which was suppressed by testosterone but elevated by antiandrogen enzalutamide. Interestingly, the results demonstrate that TNC-induced Src activation regulated AR-V7 expression, post-translational stability, and nuclear localization in prostate cancer cells. Treatment with TNC neutralizing antibody, Src knockdown, and inhibition of Src kinase activity repressed AR-V7 transcript and protein. Reciprocally, both activated Src and AR-V7 were observed to upregulate autocrine TNC gene expression in prostate cancer cells.Overall, the findings reveal that prostate cancer cell interactions with the cellular and ECM components in the osteogenic microenvironment plays critical role in regulating AR-V7 associated with metastatic CRPC.Video AbstractThe online version contains supplementary material available at 10.1186/s12964-022-00925-0. Prostate cancer is the most common non-cutaneous cancer diagnosed in men. Androgen deprivation therapies (ADT) is the mainstay treatment for advanced prostate cancer. Although ADT produce significant initial clinical response, the efficacy is short-lived as majority of patients develop castration resistant prostate cancer (CRPC) , 2. CellThe stroma is critical for normal organ development and maintaining tissue homeostasis. The stroma of solid tumors is composed of both cellular components and non-cellular extracellular matrix (ECM) –11. TumoTenascin-C (TNC), an ECM glycoprotein, is a critical component of the reactive stroma that is expressed during the earliest phase of prostate cancer development –8. ApartTNC is also expressed in metastatic niches such as the bone, lungs, lymph nodes, and functions as a chemoattractant providing a suitable milieu for disseminated tumor cells to survive and form overt tumors , 24, 25.Approximately 90% of prostate cancer patients die of bone metastases . AndrogeTNC and AR-V7 expression was induced in prostate cancer cells due to interaction with preosteoblasts. This expression was repressed by testosterone and was upregulated by estradiol and enzalutamide. Importantly, TNC functioned to stabilize AR-V7 protein post-translationally via Src activation. In a reciprocal manner, AR-V7 functioned to upregulate TNC expression. Furthermore, inhibition of Src kinase activity resulted in downregulation of both AR-V7 splicing and TNC expression in prostate cancer cells. In this context, understanding the link between bone microenvironment niche proteins such as TNC, and Src dependent AR-V7 activity provides mechanistic insight as to how this microenvironment may contribute to the evolution of CRPC. These findings may also provide insight towards therapeutic targets for AR-V7 positive, bone metastatic prostate cancer.In the present study, we developed heterotypical organoid models of human prostate cancer- osteoblast interactions to more precisely dissect gene expression and mechanisms of action. We report here that both AR−V7/pLenti was cultured in RPMI 1640 media supplemented with 10% FBS and Geneticin-G418  at a working concentration of 350 μg/ml. Addition of Doxycycline  induced AR-V7 expression. All cell lines were authenticated using short tandem repeat profiling through LabCorp  and tested regularly for mycoplasma.Human prostate cancer cells VCaP and murine preosteoblast cell line MC3T3-E1 were purchased from ATCC . In addition, 22Rv1 was also used for experiments. VCaP was cultured in high glucose DMEM media ; 22Rv1 was cultured in RPMI 1640 media ; MC3T3-E1 sub clone 4 was cultured in MEMα media . The basal media for all cell lines was supplemented with 10% fetal bovine serum and 1% Penicillin/Streptomycin antibiotic cocktail. LNCaPpLL-CMV-rFLuc-T2A-GFP-mPGK-Puro from System Biosciences, Palo Alto, CA (#LL310VA-1) to generate stable cells expressing GFP and red firefly luciferase (rFLuc) via puromycin selection  at 3ug/ml for VCaP and 5ug/ml for 22Rv1. MC3T3-E1 was transduced with pLL-CMV-RFP-T2A-Puro  to generate stable cells expressing RFP selected using puromycin at 3ug/ml.VCaP and 22Rv1 were transduced with 2 based on published protocols [Both 12 and 6 well tissue culture plates were coated with purified human TNC (Sigma # CC065) at a concentration of 75 μg/ml/0.19 cmrotocols . Bovine VCaP and 22Rv1 seeded on BSA or TNC coated plates were maintained in 5% charcoal-stripped serum (csFBS) base media. Cells were seeded at a density of 2.0E5 cells/well in 12 well plates and 4.0E5/well in 6 well plates for 72 h. RNA was extracted for analyzing gene expression and protein extracted for conducting Western blots. Cells used for confocal imaging were plated onto μ-Slide 2 Well ibiTreat slides  coated with BSA or TNC as mentioned above.Anti-Tenascin antibody was used  and AR-V7 protein level was assessed in VCaP and 22Rv1 using Western blot and confocal microscopy. The antibody isotype (#5415) from Cell Signaling Technology (CST), MA was used as a control. TNC-induced post-translational stability was assessed using cycloheximide chase assay based on published protocol . Src inhRPL30 because variance in RPL30 expression was negligible between experimental conditions. RT-qPCR was conducted for n = 3 biological replicates. Validated human specific primer sequences are listed in Additional file Co-cultures of 22Rv1/VCaP and MC3T3-E1 were seeded at a density of 2.0E5 each to form heterotypical organoids in ultra-low attachment plates. Organoid cultures were maintained in MEMα media in 5% csFBS, and 1 × P/S. Organoids were treated with vehicle control (ethanol or DMSO), testosterone (1 nM), estradiol (10 nM), or enzalutamide (10 µM) for 72 h. RNA was collected using RNeasy Mini Kit following manufacturer’s protocol . Same protocol for RNA extraction was also applied for 2D and 3D cancer cultures. Reverse transcription using amfiRivert cDNA Synthesis Platinum Master Mix  followed by qPCR via ViiA 7 system (Applied Biosystems/Life Technologies) by using FastStart Universal SYBR Green reaction mastermix  was conducted. Primer specificity (human vs mouse) was validated using SuperScript One-Step RT-PCR System (Invitrogen #10928–042). Relative transcript levels were normalized to Protein lysates were diluted in water with Laemmli buffer to a concentration of 1.5 μg/μl and separated on 6%, 8%, and 10% SDS-PAGE gels. The proteins were then transferred onto PVDF membrane followed by blocking in 5% milk dissolved in TBST. Blots were incubated in primary antibodies overnight at indicated dilutions followed by 1-h incubation in secondary antibody the next day. Antibodies used with dilutions are listed in Additional file Cell lines were transfected with small interfering RNA (siRNA) oligonucleotides using lipofectamine RNAimax (ThermoFisher Scientific # 13778075). The siRNA sequences for AR-FL and AR-V7 were designed based on previous publication and designed through Dharmacon, Horizon Discovery, Cambridge, United Kingdom . Silence0C with AR-V7 antibody. The cells were washed and incubated with secondary antibody for 1 h and nuclei were counterstained with DAPI. VCaP and 22Rv1 cells plated on TNC were treated with anti-tenascin antibody or isotype control then fixed and stained for AR-V7 using the same protocol. The specificity of AR-V7 antibody used in ICC was validated in LNCaPAR−V7/pLenti engineered with doxycycline inducible AR-V7  from Sigma. TNC antibody was conjugated to FITC (abcam # ab188285) based on recommended protocol. Organoid culture, fixing and staining protocol were adapted and modified from published protocols [Co-cultures of MC3T3-E1-RFP with 22Rv1-GFP/Luc or VCaP-GFP/Luc were seeded at a density of 2.0E5 total cells/cmrotocols , 36 and Statistical analyses were performed using GraphPad Prism 7 software. Unpaired and two-tailed students t-tests were performed where appropriate. Statistical significance was accepted at the 95% confidence level .Heterotypical organoids were developed and composed of GFP-labeled VCaP and 22Rv1 and RFP-labeled preosteoblasts. Organoids self-organized with an inner core of preosteoblasts and an outer layer of prostate cancer cells that colonize on the preosteoblasts Fig. .Fig. 1TNBoth testosterone and estradiol regulate bone homeostasis in males and females , 40. We BMPs), hedgehog ligands  with its associated receptor patched 1 (PTCH1), and transforming growth factor-beta (TGFβ)  were further stimulated by estradiol and enzalutamide and repressed by testosterone. Importantly, we excluded the gene expression from mouse-derived preosteoblasts in the organoid cultures using human specific primers  expression as the latter was either significantly repressed in VCaP or not affected in 22Rv1 in heterotypical organoids  conditions for 72 h revealed that the expression of therapeutic resistant variant was 32 fold higher in 22Rv1 compared to VCaP . This suggests that integrin β1 is the major hetero-dimerization partner for integrin αv/2/9 that can bind to TNC. To understand if TNC-induced AR-V7 post-translational stability is mediated via integrin signaling, integrin β1 was knocked down to disrupt formation of integrin heterodimers. Interestingly, knockdown of integrin β1 induced AR-V7 and TNC expression with no effect on AR-FL expression in VCaP while in 22Rv1, the knockdown resulted in suppression of AR-FL, AR-V7, and TNC expression 3/6 are known to bind to TNC and induce intracellular signaling . We obse β1 Fig. A. Integrion Fig. B. Corresion Fig. C. ContraRv1 Fig. C. These , Src knockdown downregulated AR-V7 at the protein level in both VCaP and 22Rv1 cultured on TNC, thus implicating Src as a critical mediator of TNC-induced AR-V7 post-translational stability. Interestingly, knockdown of Src suppressed TNC and AR-V7 expression in both VCaP and 22Rv1  colonization and growth on trabeculae bone . Herein,Additional file 1: Table S1. Human-Specific Primer Sequences for GenesAdditional file 2: Table S2. Antibody ListAdditional file 3: Fig. S1. Testosterone and estradiol regulate genes involved in osteogenesis. A Heat map representing the differentially regulated genes involved in osteogenesis by testosterone (1 nM) and estradiol (10 nM) in mouse preosteoblast (MC3T3-E1) using RT2 Osteogenesis PCR array.Additional file 4: Fig. S2. Gene expression analysis. A and B The effect of testosterone (1 nM) and estradiol (10 nM) on TNC expression in MC3T3-E1 confirmed by RT-qPCR and Western blot analysis. C RT-qPCR analysis of VCaP and 22Rv1 seeded on 6 well plate treated with siRNA targeting AR-FL and AR-V7. D RT-qPCR analysis of AR-FL, AR-V7, and TNC expression in VCaP and 22Rv1 plated on BSA versus TNC. N.S. represents no significance. E. Densitometric analysis of Western blot images of AR-FL expression in VCaP and 22Rv1 treated with IgG or anti-tenascin monoclonal antibody for n=3 biological replicates. Data represent mean ± SD, n=3, N.S.: Not Significant, *p<0.05, ** p<0.01 ***p<0.001, ****p<0.0001.Additional file 5: Fig. S3. Doxycycline induced AR-V7 expression in LNCaPAR-V7/pLenti . A Doxycycline inducible AR-V7 expression in LNCaPAR-V7/pLenti verified by Western blot B RT-qPCR analysis of AR-FL, AR-V7, and TNC expression in doxycycline induced LNCaPAR-V7/pLenti cell line. C ICC images of AR-V7 in LNCaPAR-V7/pLenti cells treated with Dox (2.5 ng/µl). Nuclei counterstained with DAPI . Data represent mean ± SD, n=3, * p‹0.05, ** p<0.01 ***p<0.001, ****p<0.0001.Additional file 6: Fig. S4. TNC modulates AR-V7 protein stability. A VCaP and 22Rv1 plated on BSA versus TNC in 5% csFBS containing media was treated with cycloheximide. AR-V7 band intensity was normalized to β-actin and then normalized to time=0 hr (representative prior to treatment). Data represent mean ±SD for n=3 biological replicates. B. ICC of AR-V7 nuclear localization (white arrow) in both 22Rv1 and VCaP cultured on TNC compared to BSA coated IbiTreat chamber slides. The nuclei are counterstained with DAPI. All ICC images were obtained using Nikon A1 confocal microscope . C. 22Rv1 and VCaP were cultured on TNC coated IbiTreat chamber slides followed by treatment with isotype control (IgG) or anti-tenascin monoclonal antibody at a concentration of 2.5 µg/ml (22Rv1) and 1 µg/ml (VCaP) respectively for 72 hours. The nuclei are counterstained with DAPI. All ICC images were obtained using Nikon A1 confocal microscope .Additional file 7: Fig. S5. TNC-induced increase in AR-V7 nuclear staining. A Fiji Image J quantification of AR-V7 positive nuclei in VCaP and 22Rv1 seeded on BSA versus TNC . B Fiji Image J quantification of AR-V7 nuclear intensity in VCaP and 22Rv1 seeded on BSA versus TNC . C Live cell imaging of VCaP and 22Rv1 morphology seeded on BSA versus TNC using 20 x objective. D Densitometric analysis of Western blot images depicting pFAK and pSrc activation in VCaP and 22Rv1 seeded on BSA versus TNC for n=3 biological replicates. Data represent mean ± SD, n=3,*p<0.05, ** p<0.01Additional file 8: Fig. S6. AR-FL expression with Src knockdown. A RT-qPCR following Src knockdown in VCaP and 22Rv1 plated on BSA versus TNC. N.S represents no significances. Data represent mean ± SD, n=3, ***p<0.001.


Modelos de regressão logística bruta e ajustada foram construídos para analisar associações de métricas e escores do ICVH com diagnóstico de FFA. O nível de significância foi estabelecido em 0,05.Este estudo analisou dados de 13141 participantes com dados completos. Os traçados eletrocardiográficos foram codificados de acordo com o Sistema de Minnesota, em um centro de leitura centralizado. As métricas do ICVH  e escores do ICVH foram calculados conforme proposto pela A idade mediana da amostra foi de 55 anos, e 54,4% eram mulheres. Nos modelos ajustados, os escores de ICVH não apresentaram associação significativa com diagnóstico de FFA prevalente [odds ratio (OR):0,96; intervalo de confiança de 95% (IC95%):0,80-1,16; p=0,70). Perfis de pressão arterial ideal  e colesterol total ideal  foram significativamente associados com o diagnóstico de FFA.Não foram identificadas associações significativas entre escores de ICVH global e diagnóstico de FFA após ajuste multivariado em nossas análises, devido, ao menos em parte, às associações antagônicas da FFA com métricas de pressão arterial e de colesterol total do ICVH. Nossos resultados sugerem que estimar a prevenção da FFA por meio de escore de ICVH global pode não ser adequado, e as métricas do ICVH devem ser consideradas separadamente. American Heart Association (AHA) determinou uma meta de redução da mortalidade por doença cardiovascular (DCV) e acidente vascular cerebral (AVC) em 20% em dez anos. 1 A principal estratégia para alcançar essa meta incluiu o aumento da prevalência de perfis cardiovasculares ideais, medidos por meio de sete métricas de saúde cardiovascular ideal : dieta, atividade física, tabagismo, índice de massa corporal (IMC), pressão arterial, glicose plasmática de jejum, e colesterol total. A AHA estabeleceu definições específicas para cada uma dessas métricas, bem como um escore de ICVH para um indivíduo como a soma dos perfis ideais.Em 2010, a 2 DCV clínica 3 e mortalidade cardiovascular. 4 Uma condição cardiovascular menos estudada neste contexto é a fibrilação ou o flutter atrial (FFA). A FFA tem risco de 25% de ocorrência, 5 a qual está associada a múltiplos fatores de risco cardiovascular, com uma fração atribuível à população de AVC estimada entre 2 e 6%. 8 Ogunmoroti et al. 9 analisaram dados de 6506 participantes do estudo MESA - Multi-Ethnic Study of Atherosclerosis e encontraram que indivíduos com um escore ICVH ótimo no período basal apresentaram um risco 27% mais baixo de FFA após um acompanhamento mediano de 11,2 anos em comparação àqueles com escores do ICVH inadequado. Garg et al. 10 analisaram dados de 13182 participantes do estudo ARIC ( Atherosclerosis Risk in Communities ) e encontraram que, após um seguimento de 25,1 anos, o aumento em cada componente ideal associou-se a um risco 17% menor para FFA. Análises similares foram realizadas por Garg et al. no estudo REGARDS , 11 resultando em uma redução menor (7%) porém significativa no risco para FFA para cada aumento no componente ideal. Recentemente, Lee et al. 12 analisaram 208 598 indivíduos que se submeteram a exames de check-up na Coreia do Sul e encontraram, após um seguimento mediano de 7,2 anos, que os escores do ICVH associaram-se significativamente com incidência de FFA.A eficácia dessa estratégia está sujeita à força das associações entre cada métrica de ICVH e ocorrência de DCV fatal e não fatal. Alguns autores avaliaram a associação entre escore de ICVH e seus componentes com DCV subclínica, 13 A FFA também é comum no Brasil, com frequência de aproximadamente 2% em estudos baseados na atenção primária, 14 e frequências maiores associadas ao avanço na idade.A maioria das informações sobre a associação entre FFA e métricas e escore do ICVH derivam de grandes coortes dos Estados Unidos; no entanto, estima-se que 72% dos anos de vida ajustados pela incapacidade e 67% das mortes por AVC tenham ocorrido em países com índices sociodemográficos baixos ou médios em 2016. O objetivo do presente estudo foi relatar associações do diagnóstico de FFA com métricas e escore do ICVH no Estudo Longitudinal da Saúde do Adulto (ELSA-Brasil), um estudo brasileiro multicêntrico do tipo coorte de indivíduos com idade entre 35 e 74 anos no momento basal.15 e o perfil de sua coorte 16 foram previamente descritos com detalhes. O ELSA-Brasil é um estudo multicêntrico tipo coorte em andamento no Brasil, em que foram incluídos 15105 servidores públicos ativos ou aposentados, com idade entre 35 e 74 anos, de seis instituições de seis cidades brasileiras. A avaliação basal ocorreu entre agosto de 2008 e dezembro de 2010. Nesse período, uma equipe treinada conduziu entrevistas presenciais, e exames clínicos, laboratoriais e de imagem. Após o período basal, todos os participantes eram contatados por telefone anualmente. De agosto de 2012 a dezembro de 2014, todos os participantes foram convidados para uma segunda visita, em que foram aplicados novos questionários, juntamente com avaliações clínicas e laboratoriais. Um total de 14014  indivíduos participaram dessa reavaliação. No presente artigo, as informações usadas foram obtidas dessa segunda avaliação presencial, salvo se indicado o contrário. O protocolo do estudo esteve de acordo com as normas éticas da Declaração de Helsinki de 1975 e foi aprovado pelo comitê de ética de todas as instituições participantes do ELSA-Brasil. Um termo de consentimento de todos os participantes foi obtido.O delineamento do estudo ELSA-Brasil Dos 14014 indivíduos que estiveram presentes na segunda avaliação presencial, 505 foram excluídos por falta de informação de eletrocardiograma (ECG) e 368 participantes por métricas do ICVH faltantes. Assim, nossa amostra principal consistiu em 13141 indivíduos. Para algumas análises de sensibilidade, a amostra restringiu-se a 12307 indivíduos sem relato de infarto do miocárdio, AVC ou insuficiência cardíaca prévio.18 para a avaliação de dados antropométricos, clínicos e laboratoriais não mudaram entre a primeira e a segunda avaliação. Idade, sexo, raça, nível de escolaridade, e renda familiar mensal foram autorrelatadas e estratificadas. A renda mensal foi analisada como múltiplos de salários mínimos brasileiros . Medidas de pressão arterial sistólica (PAS) e pressão arterial diastólica (PAD) foram aferidas utilizando-se um aparelho oscilométrico (Omron HEM 705 CPINT). Três medidas foram tomadas em intervalos de um minuto após um período de descanso de cinco minutos com os indivíduos sentados. A média da segunda e da terceira medida foi considerada para definição da PAS e PAD. A glicemia de jejum foi determinada pelo método da hexoquinase e o colesterol total usando o método do colesterol oxidase, realizados em um equipamento ADVIA 1200 Siemens®.Os protocolos do ELSA-Brasil 20 O ECG nas avaliações presenciais foi realizado utilizando um aparelho Burdick Atria 6100, calibrado a 10mm/mV e velocidade de 25 mm/segundo. Os registros foram transmitidos para o centro de leitura no Centro de Investigação em Minas Gerais. Os traçados foram analisados seguindo-se o sistema de Glasgow e codificados de acordo com o Sistema de Minnesota. Os códigos selecionados (incluindo FFA) foram manualmente revisados por uma equipe treinada. Esses métodos foram adotados em todas as avaliações do ELSA-Brasil até o presente. O diagnóstico de FFA neste artigo foi definido como sua presença no traçado de ECG no período basal ou na segunda visita.Os registros de ECG foram obtidos no ELSA-Brasil conforme descrito anteriormente. 21 As seguintes definições foram usadas para as sete métricas do ICVH, baseadas nas recomendações da AHA: 1Informações detalhadas sobre o sistema de escore do ICVH no ELSA-Brasil podem ser encontradas em outro estudo. Dieta: quatro componentes adequados de (a) ≥ 4 porções de frutas e verduras por dia, (b) ≥200 g de peixe por semana, (c) ≥ 2 porções de grãos integrais ricos em fibra por dia, (d) ≤ 450 kcal de bebidas adoçadas com açúcar por semana, e (e) consumo de sódio ≤1500 mg/dia;Atividade física: ≥ 75 minutos / semana ou atividade física rigorosa, ou ≥ 150 minutos / semana de atividade física moderada, ou ≥ 150 minutos / semana de atividade física moderada e atividade física vigorosa;Tabagismo: nunca ter fumado ou ter idade ao parar de fumar ao menos dois anos menor que a idade atual;2 ;IMC < 25 kg/m Pressão arterial: PAS < 120 mmHg e PAD < 80 mmHg, sem medicação anti-hipertensiva;Glicemia de jejum: < 100mg/dL sem uso de medicamentos hipoglicemiantes;Colesterol total < 200 mg/dL, sem uso de medicamentos hipolipemiantes.Todas as informações para o escore ICVH foram obtidas da segunda visita, exceto informações relacionadas à dieta. A métrica do ICVH correspondente à dieta foi avaliada a partir de informações obtidas do questionário de frequência alimentar, aplicado no momento basal do ELSA-Brasil. O escore ICVH global foi calculado como a soma de todos os perfis ideais  Escores do estilo de vida dos participantes  e saúde  foram avaliados separadamente.a posteriori , (1) excluindo indivíduos em uso de estatina, uma vez que alguns autores indicaram um benefício potencial das estatinas sobre incidência de fibrilação atrial; 23 (2) excluindo a métrica de colesterol total do escore de saúde e do escore global do ICVH. Os modelos de regressão logística binária bruta e ajustada também foram apresentados para analisar a associação entre esses escores modificados e o diagnóstico de FFA. As análises foram realizadas usando o programa R, versão 4.0.0. O nível de significância foi estabelecido em 5%.As variáveis categóricas foram apresentadas em contagens e proporções, e as variáveis contínuas em medianas e intervalos interquartis. A normalidade dos dados foi avaliada usando gráficos de densidade e o teste de Anderson-Darling. Nós calculamos a sensibilidade e a especificidade de diferentes pontos de corte do escore do ICVH global para classificar indivíduos com ou sem FFA na amostra. Construímos uma curva característica de operação do receptor (ROC) usando esses valores e calculamos a área sob a curva ROC para estimar a capacidade discriminatória dos escores do ICVH para identificar os indivíduos com FFA neste cenário. Modelos de regressão logística binária foram construídos para analisar a associação de métricas e escores do ICVH  com o diagnóstico de FFA. Esses modelos foram apresentados na forma bruta ou ajustada quanto à idade, sexo e raça. Foram feitas análises de sensibilidade restringindo a amostra a indivíduos sem relato de história de infarto do miocárdio, AVC ou insuficiência cardíaca. Após observar uma associação paradoxal entre a métrica doo ICVH de colesterol total e FFA, realizamos algumas análises Tabela 1 Suplementar apresenta as características dos participantes do estudo após exclusão daqueles com história de infarto do miocárdio, AVC ou insuficiência cardíaca.A Figura Suplementar 1 apresenta a curva ROC referente à acurácia dos escores de ICVH global em identificar indivíduos com FFA na amostra. A área sob a curva ROC é 0,59, indicando um poder discriminatório relativamente baixo dos escores de ICVH global neste cenário. Mais detalhes são apresentados na Tabela Suplementar 2 , que mostra valores de sensibilidade e especificidade para diferentes pontos de corte do escore de ICVH global.A odds ratio (OR) e respectivos intervalos de confiança (IC95%) para a associação de escores e métricas de ICVH com prevalência de FFA. Em toda a amostra, os escores de ICVH foram inversamente associados com o diagnóstico de FFA no modelo bruto  e no modelo ajustado . A exclusão dos indivíduos em uso de estatina das análises levou a uma perda de significância da associação entre o perfil de colesterol total no ICVH e a FFA nos modelos ajustados . Contudo, essa perda de significância parece ser devida principalmente a uma perda de poder estatístico, uma vez que 46,2% dos participantes com FFA e 51,0% dos participantes sem FFA usavam estatinas.A Uma vez que as associações da FFA com a pressão arterial e a métrica de colesterol total do ICVH eram antagônicas, a FFA não se associou com escore de ICHV global nos modelos ajustados (p=0.76). Após exclusão de indivíduos com relato de infarto do miocárdio ou insuficiência cardíaca prévia, as associações da FFA com pressão arterial (p=0.023) e métrica de colesterol total do ICVH  nos modelos ajustados foram mantidas.Também verificamos se os escores de saúde e os escores de ICVH global foram associados com FFA após exclusão da métrica de colesterol total. O escore de ICVH global mostrou-se inversamente associado com um diagnóstico de FFA nos modelos brutos  com uma tendência não significativa a uma associação inversa nos modelos ajustados . Os escores de saúde do ICVH foram inversamente associados com um diagnóstico de FFA no modelo absoluto  e no modelo ajustado .Na amostra do ELSA-Brasil, os escores de ICVH global foram associados com prevalência de FFA nos modelos brutos. No entanto, os escores foram ajustados com valores de área sob a curva ROC e a significância estatística desapareceu nos modelos ajustados para idade, sexo e raça. Analisando as métricas de ICVH separadamente, encontrou-se uma forte associação inversa entre a métrica de pressão arterial do ICVH e a FFA. Uma associação positiva, mas paradoxal, foi observada entre métrica de colesterol total do ICVH e FFA: uma métrica de colesterol total ideal do ICVH foi associada com diagnóstico de FFA. A restrição da amostra para indivíduos sem relato de infarto do miocárdio, AVC ou insuficiência cardíaca levou a resultados similares. A exclusão da métrica do colesterol total do ICVH levou a uma associação inversa significativa entre escores de saúde do ICVH e FFA.24 revisaram dados de 32 estudos de coortes de base populacional, incluindo mais de 20 milhões de indivíduos. Os autores encontraram que o diagnóstico de hipertensão e pressão arterial sistólica elevada foram consistentemente associados com incidência de FFA. Recentemente, Rattani et al. 25 utilizaram dados do estudo ARIC para calcular o risco atribuível na população de hipertensão para FFA. Os autores definiram hipertensão de acordo com os critérios do Sétimo Relatório do Joint National Committee (≥140/90 mmHg) e as diretrizes da American Heart Association/American College of Cardiology de 2017 (≥130/80 mmHg), e encontraram valores de fração atribuível populacional de 11% e 13%, respectivamente. Como esperado, a presença de um perfil ideal de pressão arterial também foi inversamente associada à FFA nos estudos de tipo coorte ARIC, 10 REGARDS, 11 e MESA. 9A importância da hipertensão como um fator de risco para FFA está bem definida na literatura. Em uma revisão sistemática de fatores de risco para FFA Allan et al. 27 ou mesmo indivíduos de amostras da comunidade. 28 Em uma revisão sistemática recente, Guan et al. 29 encontraram que níveis elevados de colesterol total  foram associados a uma razão de risco agrupado ( pooled hazard ratio ) para FFA de 0,81 , o que foi consistente como nossos achados. Na mesma revisão sistemática, análises utilizando níveis de LDL-colesterol em vez de níveis de colesterol total mostraram resultados similares.Embora o colesterol total  seja um fator de risco importante para DCV aterosclerótica, sua associação com FFA não é tão bem estabelecida. Outros autores indicaram o paradoxo do colesterol na FFA, descrevendo níveis mais baixos de colesterol em indivíduos com FFA, em comparação a controles em vários cenários, tais como indivíduos tratados em centros de atenção primária, 23 No entanto, a métrica do ICVH considera um perfil como não ideal se os indivíduos estão em uso de medicamentos hipolipemiantes, independentemente de seus níveis de colesterol total. Portanto, poderia ser argumentado que a associação paradoxal entre perfil de ICVH quanto ao colesterol total e FFA é explicada pelo uso de estatina; porém, nossos dados sugerem que esse não é o caso. A proporção de indivíduos de nossa amostra usando medicamentos hipolipemiantes é similar. Ainda, embora a exclusão de indivíduos que usam estatinas tenha levado à perda de significância estatística, isso provavelmente tenha ocorrido pelo elevado número de exclusões dessa análise de sensibilidade , uma vez que as estimativas do OR também eram similares .Existem evidências de que as estatinas possam tem potencial benefício sobre a incidência de fibrilação atrial. 11 que avaliaram os escores de ICVH e sua relação com diagnóstico de FFA também investigaram a métrica de colesterol total do ICVH separadamente. Em todos os casos, as estimativas do risco sugeriram maior chance para FFA nos indivíduos com colesterol total ideal, mas sem diferença estatisticamente significativa. Essa ausência de significância nesses estudos contrasta com nossos achados de uma associação significativa, positiva, mas paradoxal entre a métrica de colesterol total ICVH e o diagnóstico de FFA nos modelos ajustados. Essa associação estatisticamente significativa em nosso estudo foi evidente mesmo com menos casos de FFA na amostra, em comparação a publicações anteriores. Diferenças de populações e delineamento dos estudos, podem ser parcialmente responsáveis por tal discrepância. Similar ao que se observa nos Estados Unidos, indivíduos brasileiros da raça negra apresentam uma prevalência maior de hipertensão 30 e uma prevalência mais baixa de dislipidemia 31 em comparação aos de raça branca. Dada a forte associação inversa entre pressão arterial e FFA, poderia ser argumentado que a raça seria um fator de confusão na associação positiva entre perfil de colesterol total do ICVH e diagnóstico de FFA. No entanto, é importante notar que nossos resultados se mantiveram mesmo após o ajuste por raça. Análises longitudinais futuras do ELSA-Brasil, incluindo a ocorrência de mais casos de FFA, irá esclarecer se o paradoxo do colesterol em indivíduos com FFA é particularmente forte na população brasileira.O critério usado como a métrica de colesterol total do ICVH (<200 mg/dL sem uso de hipolepimantes) é mais rígido que aqueles adotados nos estudos incluídos nesta revisão sistemática. Os estudos coorte 32 propuseram que o uso do escore ICVH para melhorar a saúde cardiovascular global pode reduzir substancialmente a prevalência de FFA. Embora evidências atuais sugiram que tal fato seja verdadeiro, nossos resultados e dados prévios também destacam que métricas individuais do ICVH podem ter efeitos diferentes (e mesmo antagônicos) sobre a prevalência da FFA. Assim, é discutível se o progresso na prevenção da FFA resultante não só de melhorias nos escores do ICVH devam ser estimadas considerando não só o impacto de todas as métricas do ICVH em conjunto como também cada métrica separadamente.Em 2018, Isakadze et al. 19 e os critérios de escore do ICVH pôde ser aplicado com mínimas adaptações.O presente estudo tem pontos fortes. Primeiro, o estudo avaliou dados de uma grande amostra no Brasil. Em nosso conhecimento, este é o primeiro estudo a analisar a associação entre FFA e métricas do ICVH em uma amostra da América do Sul com diferentes características comparadas às amostras analisadas em estudos prévios. Os traçados de ECG também foram analisados em um local de leitura centralizado, usando um protocolo padronizado, 21 que é consistente com os achados de outras populações. 33 Assim, é improvável que uma grande proporção de participantes teria adotado uma dieta ideal entre o período basal e a segunda visita. A FFA foi definida com base somente nos traçados de ECG do ELSA-Brasil e, apesar de conferir alta especificidade, FFA paroxística pode ser pouco representada em nossas análises.O estudo também precisa ser interpretado no contexto de suas limitações. A amostra deste estudo incluiu um pequeno número de participantes com FFA. Isso deve-se muito provavelmente à alta proporção de indivíduos com idade inferior a 60 anos de idade. Com o passar do tempo, os casos incidentes de FFA podem aumentar o poder de nossas análises. Isso pôde ter influenciado nosso resultado de não associação entre diagnóstico de FFA e escores de ICVH. O questionário de frequência alimentar não foi aplicado na segunda visita dos participantes no estudo ELSA-Brasil; portanto, considerou-se que os participantes mantiveram o status de dieta no ICVH após o basal. A prevalência de uma dieta ideal (segundo critérios do ICVH) foi muito baixa no período basal do ELSA-Brasil , Não foram observadas associações significativas entre escores de ICVH global e diagnóstico de FFA em nossas análises, devido, ao menos em parte, às associações antagônicas de FFA com pressão arterial e colesterol total. Nossos resultados sugerem que estimar o efeito da prevenção de FFA usando escores de ICVH global pode não ser adequado, e as métricas do ICVH devem ser consideradas separadamente. 1 The main strategy to achieve this goal included raising the prevalence of ideal cardiovascular profiles, measured by seven ideal cardiovascular health (ICVH) metrics: diet, physical activity, smoking, body mass index (BMI), blood pressure, fasting plasma glucose, and total cholesterol. The AHA established specific definitions for each of these metrics, as well as a ICVH score for an individual as the sum of the ideal profiles.In 2010, the American Heart Association (AHA) set a decade-long goal to decrease cardiovascular disease (CVD) and stroke mortality by 20%.2 clinical CVD3 and cardiovascular mortality.4 A less studied cardiovascular condition in this context is atrial fibrillation or flutter (AFF). AFF has a lifetime risk of 25%,5 is associated with multiple cardiovascular risk factors, and is a major risk factor for stroke, with population attributable fractions of stroke estimated between 2% and 6%.8 Ogunmoroti et al.9 analyzed data from 6,506 participants from the Multi-Ethnic Study of Atherosclerosis (MESA) and found that individuals with an optimum ICVH score at the baseline had a 27% lower risk of AFF after a median follow-up of 11.2 years as compared to those with inadequate ICVH scores. Garg et al.10 analyzed data from 13,182 Atherosclerosis Risk in Communities (ARIC) participants and found that, after a follow-up of 25.1 years, each ideal component increase was associated with a 17% lower risk for AFF. Similar analyses were also performed by Garg et al. in the Reasons for Geographic and Racial Differences in Stroke Study (REGARDS),11 resulting in a smaller (7%) although significant reduction in the risk for AFF for each ideal component increase. Recently, Lee et al.12 analyzed 208,598 individuals who underwent national health check-up examinations in South Korea and found, after a median follow-up of 7.2 years, that ICVH scores were significantly associated with incident AFF.The effectiveness of such a strategy is subject to the strength of the associations between each ICVH metric and occurrence of fatal or non-fatal CVD. Some authors evaluated the association of the ICVH score and its components with subclinical CVD,13 AFF is also common in Brazil, with a frequency of about 2% in primary care-based studies,14 with higher frequencies associated with advancing age.Most information about the association between AFF and ICVH metrics and score come from large cohorts in the United States; however, 72% of global disability-adjusted life-years and 67% of deaths due to stroke were estimated to occur in countries with middle or low sociodemographic index in 2016.The aim of the present study is to report the associations between AFF diagnosis and ICVH metrics and score in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), a Brazilian multicenter cohort study of individuals of 35-74 years of age at the baseline.15 and cohort profile16 are detailed elsewhere. ELSA-Brasil is an ongoing multicenter cohort study in Brazil which enrolled 15,105 active or retired civil servants, from 35 to 74 years of age at baseline, from six institutions in six Brazilian cities. Baseline assessment occurred between August 2008 and December 2010. During this period, trained staff conducted in-person interviews, as well as clinical, laboratory, and imaging exams. After the baseline, all participants received a yearly telephone follow-up contact. From August 2012 to December 2014, all participants were invited to a second visit, during new questionnaires were administered, together with clinical and laboratory evaluations. A total of 14,014 (92.8%) individuals were reassessed. In the present article, information was obtained from the second visit, unless stated otherwise. The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki and was approved by the Institutional Review Boards of all institutions where ELSA-Brasil investigation centers are located. Informed consent was obtained from each participant.The ELSA-Brasil designFrom 14,014 individuals who were present in the second onsite assessment, 505 individuals were excluded due to a lack of electrocardiographic (ECG) information and 368 participants due to missing information on ICVH metrics. Therefore, our main sample consisted of 13,141 individuals. For some sensitivity analyses, the sample was restricted to 12,307 individuals without previous self-reported myocardial infarction, stroke, or heart failure.18 for anthropometric, clinical and laboratory exams did not change between the first and second assessments. Age, sex, race, education level, and monthly family income were self-reported and stratified accordingly. Monthly income was analyzed as multiples of the Brazilian minimum wage (one Brazilian minimum wage during data collection averaged approximately 310 US dollars). Systolic and diastolic blood pressure  measurements were taken using a validated oscillometric device (Omron HEM 705CPINT). Three measurements were taken at one-minute intervals after a five-minute rest with the subject in the sitting position, and the average of the second and third measurements was considered to define SBP and DBP. Fasting plasma glucose was determined using the hexokinase method and total cholesterol using the cholesterol oxidase method, conducted in an ADVIA 1200 Siemens® equipment.ELSA-Brasil protocols20 Electrocardiography in onsite assessments was performed using a Burdick Atria 6100 device, calibrated at 10 mm/mV and a speed of 25 mm/second. The recordings were transmitted to the reading center in the Minas Gerais Investigation Center. Analyses followed the Glasgow system and were coded according to the Minnesota Coding System. Selected codes (including AFF) were manually reviewed by trained staff. These methods have been adopted in all ELSA-Brasil assessments to date. AFF diagnosis in this article was defined as its presence in ECG tracing at the baseline or on the second visit.ECG recordings in ELSA-Brasil were obtained as described elsewhere.21 The following definitions were used for the seven ICVH metrics, based on the AHA guidelines:1Detailed information about the ideal ICVH scoring in ELSA-Brasil can be found elsewhere.Diet: Four adequate components from (a) ≥ 4 servings of fruit and vegetables per day, (b) ≥ 7 ounces of fish per week, (c) ≥ 2 servings of fiber-rich whole grains per day, (d) ≤ 450 kcal of sugar-sweetened beverages per week, and (e) sodium consumption ≤ 1500 mg/day;Physical activity: ≥ 75 minutes/week of vigorous physical activity, or ≥ 150 minutes/week of moderate physical activity, or ≥ 150 minutes/week of moderate + vigorous physical activity;Smoking: never smoked or former smoker age upon quitting of at least two years less than the age at onsite assessment;2 ;BMI < 25 kg/mBlood pressure: SBP < 120 mmHg and DBP < 80 mmHg, without antihypertensive medication;Fasting plasma glucose: < 100 mg/dL, without hypoglycemic medication;Total cholesterol: < 200 mg/dl, without lipid-lowering medication.All information for ICVH scoring was obtained from the second visit, except for the diet ICVH metric. The diet ICVH metric was evaluated using information from the complete food frequency questionnaire, which was applied in the ELSA-Brasil baseline. The global ICVH score was calculated as the sum of the ideal profiles (range: 0 to 7 points). Scores of participants’ lifestyle  and health  were evaluated separately.a posteriori, (1) excluding individuals under statin use, as some authors pointed a potential benefit of statins on incident atrial fibrillation;23 (2) excluding the total cholesterol ICVH metric from the global and health ICVH scores. The crude and adjusted binary logistic regression models were also presented in order to analyze the association between these modified scores and AFF diagnosis. Analyses were performed using R software, version 4.0.0. The significance level was set at 5%.Categorical variables were presented as counts and proportions, and continuous variables were presented as medians and interquartile ranges. Normality of data was evaluated using density plots and the Anderson-Darling test. We calculated the sensitivity and specificity of different cutoffs for global ICVH score to classify individuals with and without AFF in the sample. We plotted a receiver-operating characteristic (ROC) curve using these values and calculated the area under the ROC curve (AUROC) to estimate the discriminative capacity of the global ICVH scores to identify individuals with AFF in this setting. Binary logistic regression models were built to analyze the association of ICVH metrics and global, lifestyle, and health scores with AFF diagnosis. These models are presented in their crude form and adjusted for age, sex, and race. Sensitivity analyses were performed, restricting the sample to the individuals without previous self-reported myocardial infarction, stroke, or heart failure. After observing a paradoxical association between the total cholesterol ICVH metric and AFF, we ran some analyses Supplemental Table 1 shows the characteristics of study participants after excluding those with previous self-reported myocardial infarction, stroke, or heart failure.Supplemental Figure 1 shows the ROC curve addressing the accuracy of global ICVH scores in identifying individuals with AFF in the sample. The AUROC is 0.59, indicating a relatively low discriminatory power of global ICVH scores in this scenario. More details are shown in the Supplemental Table 2 , which displays sensitivity and specificity values for different global ICVH score cutoffs.As the associations of AFF with blood pressure and total cholesterol ICVH metrics were antagonistic, AFF was not associated with an overall health ICVH score in adjusted models (p=0.76). After excluding individuals with self-reported myocardial infarction, stroke, or heart failure, the associations between AFF and blood pressure (p=0.023) and total cholesterol ICVH metrics (p=0.007) in adjusted models remained.We also verified whether the global and/or health ICVH scores were associated with AFF after the exclusion of the total cholesterol ICVH metric. The global ICVH score was shown to be inversely associated with an AFF diagnosis in crude models  with a non-significant trend towards an inverse association in adjusted models . Health ICVH scores were inversely associated with an AFF diagnosis in both crude  and adjusted  models.In the ELSA-Brasil sample, global ICVH scores were associated with prevalent AFF in crude models. However, they were associated with low AUROC values and statistical significance disappeared in models adjusted for age, sex, and race. Analyzing ICVH metrics separately, a strong inverse association was found between the blood pressure ICVH metric and AFF. A positive but paradoxical association was observed between the total cholesterol ICVH metric and AFF: an ideal total cholesterol ICVH metric was associated with AFF diagnosis. The restriction of the sample to individuals with no self-reported myocardial infarction, stroke, or heart failure yielded similar results. The exclusion of the total cholesterol ICVH metric led to a significant inverse association between health ICVH scores and AFF.24 reviewed data from 32 population-based cohorts, including more than 20 million subjects. The authors found that the diagnosis of hypertension and high systolic blood pressure were consistently associated with incident AFF. Recently, Rattani et al.25 used data from the ARIC study to calculate the population attributable risk of hypertension for AFF. The authors defined hypertension according to the criteria from the 7th Report of the Joint National Committee (≥140/90 mmHg) and the 2017 American Heart Association/American College of Cardiology guidelines (≥130/80 mmHg), and found population attributed fraction values of 11% and 13%, respectively. Expectedly, the presence of an ideal blood pressure profile was also inversely associated with AFF in the ARIC,10 REGARDS,11 and MESA9 cohort studies.The importance of hypertension as a risk factor for AFF is well defined in the literature. In a systematic review of risk factors for incident AFF, Allan et al.27 or even those from community samples.28 In a recent systematic review, Guan et al.29 found that high levels of total cholesterol  were associated with a pooled hazard ratio for AFF of 0.81 (95% CI: 0.72-0.92), which was consistent with our findings. In the same systematic review, analyses using LDL-C instead of total cholesterol levels yielded similar results.Although total cholesterol  is a major risk factor for atherosclerotic cardiovascular disease, its association with AFF is much less clear. Other authors have pointed to the cholesterol paradox in AFF, describing lower cholesterol levels in individuals with AFF, upon comparing controls in diverse scenarios, such as individuals treated in referral centers for other cardiovascular diseases, those treated in primary care units,23 However, the ICVH metric considers as a non-ideal profile if the individual is under lipid-lowering medications, regardless of his/her total cholesterol levels. Therefore, it could be argued that the paradoxical association between total cholesterol ICVH profile and AFF is explained by statin use. Our data suggest this is not the case. The proportion of individuals in our sample using lipid-lowering medication is similar. Moreover, although the exclusion of individuals under statins led to a loss of statistical significance, this was probably due to the high number of exclusions from this sensitivity analysis (51.0% of our sample), as the OR point estimates were also similar There is some evidence that statins may have a potential benefit on incident atrial fibrillation.11 that evaluated ICVH scores and their relationship with AFF diagnosis have also studied the total cholesterol ICVH metric separately. In all cases, the hazard point estimates suggested higher odds for AFF in individuals with ideal total cholesterol, but without statistical significance. Their non-significant results contrast to our finding of a significant, positive, but paradoxical association between the total cholesterol ICVH metric and AFF diagnosis in adjusted models. This significant association in our study was evident even with less AFF cases in the sample, when compared to these previous publications. Differences in study populations and design may be partly responsible for this discrepancy. Similar to the United States, black Brazilians have a higher prevalence of hypertension30 and a lower prevalence of dyslipidemia,31 when compared to white Brazilians. It could be argued, given the strong inverse association between blood pressure and AFF, that race could be a confounder in the positive association between a total cholesterol ICVH profile and AFF diagnosis. However, it is important to note that our results were maintained even after adjustment for race. Future longitudinal analyses from the ELSA-Brasil, including the occurrence of more AFF cases, will clarify if the cholesterol paradox in individuals with AFF is particularly strong in the Brazilian population.The criterion used as the total cholesterol ICVH metric (<200 mg/dL without lipid-lowering medication use) is stricter than those in the studies included in this systematic review. The cohort studies32 proposed that the use of the ICVH score to improve overall cardiovascular health may substantially reduce AFF prevalence. Although current evidence suggests this is probably true, our results and previous data also point out that individual ICVH metrics may have different (and even antagonistic) effects on AFF prevalence. Therefore, it is arguable that the progress in AFF prevention resulting from improvements in ICVH scores must be estimated considering not only the impact of all ICVH metrics together but also of each metric separately.In 2018, Isakadze et al.19 and the ICVH score criteria could be applied with minimal adaptations.The present study has strengths. First, it evaluated data from a large sample in Brazil. To our knowledge, this is the first study to analyze the association between AFF and ICVH metrics in a South American sample with different characteristics compared to the samples analyzed in previous studies. ECG tracings were also analyzed in a centralized reading center, using a standardized protocol,21 which is consistent with the findings from other populations.33 Therefore, it is unlikely that a large proportion of participants would have adopted an ideal diet between the baseline and the second onsite assessment. The AFF was defined based only on ECG tracings of the ELSA-Brasil and, although this ensures high specificity, paroxysmal AFF may be underrepresented in our analyses.This study also needs to be interpreted in the context of its limitations. The sample of this study included a small number of AFF participants. This is most probably due to its high proportion of individuals of less than 60 years of age. As time progresses, incident AFF cases may increase the power of our analyses. This may have influenced our finding of non-association between AFF diagnosis and ICVH scores. The food frequency questionnaire was not applied in the second visit of patients in the ELSA-Brasil; therefore, it was considered that participants maintained their diet ICVH status after the baseline. The prevalence of an ICVH diet was very low in the ELSA-Brasil baseline (1.3%),In conclusion, no significant associations were observed between global ICVH scores and AFF diagnosis in our analyses, at least partially due to antagonistic associations of AFF with blood pressure and total cholesterol. Our results suggest that estimating the AFF prevention effect using global ICVH scores may not be adequate, and ICVH metrics should be considered in separate.


With the demand for rehabilitation has been increasing faster for the aging of China's population, the equity of rehabilitation resource has aroused great concern. This study aimed to analyze the spatial distribution and evolution of the human resources of rehabilitation institutions and propose targeted countermeasures and suggestions to promote optimal allocation.A total of 31 provinces in China Mainland were identified and geocoded. The spatial weight matrix was introduced to analyze the spatial correlation. Spatial autocorrelation analysis and tests were used to analyze the spatial distribution and evolution characteristics of rehabilitation institutions' human resources in China from 2016 to 2019.P > 0.05). Three provinces in western China belonged to the Low-Low area and a province in northeastern China fitted to the Low–High area, with statistically significant differences. In addition, the changes in the spatial distribution and evolution trend of the human resources of rehabilitation institutions in different periods were affected by health policies.The average density of rehabilitation staff from 2016 to 2019 has been rising yearly (From 1.60 to 1.88). From 2018 to 2019, the proportion of rehabilitation professionals was higher than 75% in only 5 provinces, and no provinces met 75% from 2016 to 2017. Global Moran's I index from 2016 to 2019 showed no apparent aggregation phenomenon in the allocation of management personnel resources (Although the overall spatial distribution gap of human resource allocation of rehabilitation institutions is shrinking, there are still internal structural defects and a maldistribution at the provincial level. It is necessary to improve the overall number of staff in rehabilitation institutions and to ameliorate the proportion of different types of staffing. The demand for rehabilitation in China has been continuously growing due to the aging of China's population, the prevalence of chronic non-communicable diseases and unhealthy lifestyles . It is cRehabilitation is an essential healthcare service for persons who are with a variety of medical issues. In addition to being the most efficient means to improve the physical state of people with disabilities, aid from rehabilitation institutions in staff is also the most effective way to increase their capacity for social adaptation. Rehabilitation for individuals with disabilities demonstrates a state's concern and attention for vulnerable groups like the disabled and the degree of society's overall development. Rehabilitation institutions and their human resources are the core elements that facilitate improved rehabilitation systems for the disabled. The availability of rehabilitation institutions, as well as their overall density, internal structure, and layout, is not only an important standard to measure the development level of rehabilitation services but also a reference basis for governments to propose targeted countermeasures and relevant policies .Human resources in rehabilitation institutions still encounter challenges, including regional inequality and unbalanced development, although the state of rehabilitation technology in China has steadily risen. There is increasing interest in inequality in the context of the public health realm. Existing studies mainly focus on the following topics:Specific rehabilitation issues, including comprehensive cardiovascular rehabilitation  and the Medical and health resource maldistribution, including the differences between urban and rural areas  and examTraditional research methods for the maldistribution or equity of health and medical resources, such as the Gini coefficient , Theil iDue to the lack of academic attention for rehabilitation human resource maldistribution, few studies concentrate on rehabilitation institutions' human resource maldistributions, especially in spatial research. The Theil index and health resource density index (HRDI), sensitive indices in evaluating the equality of resource allocation, have been used to explore the allocation of rehabilitation resources . HoweverWe sought to answer increasingly complex questions rooted in social situations: What are the provincial trends, conditions, and maldistribution of human resources in China for rehabilitation? Are changes in rehabilitation human resource allocation affected by essential policies or important national conferences? In order to fully explore the trends and distribution of rehabilitation resources in various provinces of China, this study uses the provincial administrative regions as research units to express the spatial distribution and evolution characteristics of human resources of rehabilitation institutions at the provincial level from 2016 to 2019 visually through a geographic information system in order to encourage the steady development of rehabilitation in China and the rational use of resources, as well as offering suggestions for policymakers.Rehabilitation professionals can be divided into three categories. They are Staff in Rehabilitation Institutions (SRI), Professionals (P), and Managerial Personnel (MP). In this study, we used “density” to analyze the distribution of human resources. The staff in rehabilitation institution density (SRID) represents the number of staff in rehabilitation institutions divided by population and multiplied by 10,000 ; professionals density (PD) represents the number of professionals divided by population and multiplied by 10,000 ; and managerial personnel density (MPD), represents the number of managerial personnel divided by population and multiplied by 10,000 . The proportion of professionals (PP), which means the number of professionals divided by SRI (Unit: %), was also considered as an indicator for the guidance of the China Disabled Persons' Federation and the principle of post-structure proportion of professional and technical personnel in medical institutions (PRINCIPLE) formulated by Ministry of Health, PRC.According to geographical location and gross domestic product per capita, provinces are grouped as belonging to three regions: the western, central, and eastern regions, representing the undeveloped, developing, and developed regions in China Mainland, respectively. The eastern region includes Beijing, Tianjin, Hebei, Liaoning, Shanghai, Jiangsu, Zhejiang, Fujian, Shandong, Guangdong, and Hainan. The central region includes Shanxi, Jilin, Heilongjiang, Anhui, Jiangxi, Henan, Hubei, and Hunan. The western area includes Inner Mongolia, Guangxi, Chongqing, Sichuan, Guizhou, Yunnan, Tibet, Shaanxi, Gansu, Qinghai, Ningxia, and Xinjiang.The purpose of this study was to investigate the trends, spatial distribution, and evolution characteristics of human rehabilitation resources in China and to give evidence for policy decisions. To focus on the distribution of rehabilitation human resources in China under the background of Healthy China 2030, which was promulgated in 2016 and considers data availability, the analysis period started in 2016 and ended in 2019, the year of the latest available data.We used the official statistics released by the China Statistical Yearbook on the Work for Persons with Disabilities (CSYWPDs) , which pSpatial autocorrelation was used to analyze the tendency of spatial clustering of human resources in rehabilitation.Rook criterion using the conventional method, holding that the weight is defined as 1 when two areas share a boundary but is valued at 0 otherwise  was formed using GeoDa software (Version 1.16.0.12). We constructed our SBWM with the therwise . Howevertherwise , 19. TabGlobal spatial autocorrelation (GSA) is the spatial feature description of the characteristics related to resource (such as human resources) allocation in a whole specified area . Global i and xj represent the observations of rehabilitation staff on space units i and j, respectively. wij represents SBWM with the Rook criterion, and n represents the total number of provinces   . For the n = 31) . The forp < 0.05 in this study is significant), strong positive spatial correlation of human resources in rehabilitation institutions among provinces will appear if I is > 0 and closer to 1. If I is < 0 and closer to −1, it indicates that the negative spatial correlation between provinces is stronger. There is no spatial autocorrelation between provinces when I is 0  often use the Local Moran's I index to capture important spatial patterns of clustering and dispersion at a local scale between local adjacent provinces and test the significance level . The prii and xj represent the observations of rehabilitation staff on space units i and j, respectively. wij represents SBWM with the Rook criterion. ith provincial unit, and m is the number of neighboring provinces of provincial unit i . Furthermore, n represents the total number of provinces . LSIA maps were drawn based on the Z-score significance level test under the predetermined significance level (p < 0.05 in this study is significant).In the above formula, xp40mm The Local Moran's I analysis results include four significant types that may be shown in LISA maps based on the size of the observed values: High–High type (HH), Low–Low type (LL), High–Low type (HL), Low–High type (LH), and one type with no significant difference (NG) . Each tyIBM SPSS 26.0 was used for descriptive statistics to determine the number of human resources in rehabilitation institutions and the category composition of staff based on the number of people and service areas. Origin 2018 software was used to draw spatial Moran's I index curve maps.cSRID, PD, and MPD from 2016 to 2019 are shown in SRID, PD, and MPD in Jilin all belonged to “Highest density ” areas while the three categories of staff in Qinghai and Tibet were all “Lowest density” areas from 2016 to 2019. The average SRID in China were 1.60, 1.76, 1.78, and 1.88 from 2016 to 2019, the average PD were 1.08, 1.18, 1.26, and 1.35 from 2016 to 2019, and the average MPD were 0.21, 0.22, 0.21, and 0.21 from 2016 to 2019. Other basic information can be seen in 5–8).The PRINCIPLE recommended that the proportion of professionals in rehabilitation institutions should reach 75%. From 2016 to 2017, no province met the PRINCIPLE's requirements. In 2018, five Chinese provinces' PPs were higher than 75%. They were Anhui (76.7%), Shandong (77.5%), Henan (78.6%), Hainan (76.1%), and Shaanxi (75.3%). In 2019, there were also five Chinese provinces' PPs higher than 75%. However, it was not totally the same provinces as in 2018, and they were Anhui (81.6%), Henan (78.5%), Ningxia (78.2%), Shandong (77.1%), and Shaanxi (76.7%), mainly non-coastal provinces. Among the 26 provinces below the recommended proportion, Jiangsu and Shanxi Provinces were close to reaching the standard of 75% (both 74.9%), and Shanghai (52.5%) had the lowest proportion (More details could be found in p > 0.05), which means there was no apparent aggregation phenomenon in the allocation of MP resources.The changes in Global Moran's I index from 2016 to 2019 are shown in The LISA significance test showed the provincial spatial unit attributes of rehabilitation personnel and their interaction with adjacent provinces in China from 2016 to 2019.It could be clearly seen that the distribution of SRI resources in China has been relatively consistent as a whole in the past 4 years , althougThe LISA test results also showed a difference between SRID, PD, and MPD in the same year. Comparing the SRID and PP in rehabilitation institutions from 2016 to 2019 can reflect the changes in the internal structure of rehabilitation staff in the past four years to a certain extent. With the SRID as the horizontal axis and PP as the vertical axis, the scatter plot with four quadrants was drawn using Origin 2018 software. The four quadrants have the following meanings:In the first quadrant, the SRID of the province is higher than the national average, and the PP is higher than the PRINCIPLE's recommendation. For the second quadrant, the PP meets the suggestion of the PRINCIPLE, but the SRID is lower than the national average. The SRID is lower than the national average, and the PP is lower than the PRINCIPLE of advice in the third quadrant. As for the fourth quadrant, the SRID is higher than the national average, but the PP is lower than the requirements in the PRINCIPLE. The scatter plot is displayed in From 2016 to 2017, there was no province in the first and second quadrants, as they were mainly scattered in the third and fourth quadrants and gradually “migrated” from the third quadrant to other quadrants over time. That is, the PP in an increasing number of provinces has begun to meet the PRINCIPLE, or the SRID has been reaching the national average. From 2018 to 2019, Shandong and Shaanxi, which were distributed in the first quadrant, took the lead in meeting the two standards. The western region was mostly concentrated in the third quadrant, which means these provinces failed to meet the two indicators. The eastern and central regions were mostly concentrated near the two axes, which suggested that the staffing of these provinces was close to the national average. Over the past 4 years, the average value of the SRID in China has been gradually increasing . It should be pointed out that the position of Tibet and Shanghai in the scatter plot did not change. When the PP was also low in these two provinces, the SRID showed the opposite phenomenon of one being high (Shanghai) and one being low (Tibet).This was a nationwide study that comprehensively evaluated the trend of allocation of human resources in China's rehabilitation institutions by longitudinal and horizontal comparison. Rehabilitation is a fundamental health service for people with a variety of health conditions, and it primarily focuses on improving their ability to function well in society and on reducing the impact of disability .From the perspective of the whole country, there were certainly regional differences between provinces in 2019, regardless of whether SRID, PD, or MPD was examined, with a massive gap of approximately 16 times between the highest and lowest provinces. As far as the provincial level is concerned, Tibet was the worst, as its SRID was only 0.22, which suggests that local residents are not able to obtain rehabilitation resources on time.In the meanwhile, the internal staff structure of rehabilitation institutions also needs to be improved. According to the examination of this study, from 2016 to 2017, no province implemented the PRINCIPLE's recommendation for the PP. Although this phenomenon has been ameliorated in the past 2 years, the number of qualified provinces remained low , which suggests that there may be some defects in the staff structure in all provinces, for example, the number of SRI being insufficient or there being too many MPs and other personnel. Determining how to increase the PP to improve maldistribution appropriately is a task that needs further attention in some provinces.Therefore, relevant solutions and schemes should be considered at the national level to improve the PP in rehabilitation institutions in different provinces. For policy formulation and implementation, we should focus more attention on the following points:(1) While the spatial gap of human resources in rehabilitation institutions has been gradually narrowing, the SRID in western China has maintained a low level, which may indicate the lack of rehabilitation resources and severe brain drain in western China.(2) Those provinces where the PP does not meet the principles should pay attention to the adjustment of personnel internal structure, balance workload and efficiency, give consideration to quantity and structure, and further optimize the human resource allocation of rehabilitation institutions while expanding the number of SRI.The trend of the Global Moran's I index reflected that although the difference in human resources allocated by the regional area of rehabilitation institutions in China was small, the spatial autocorrelation of human resources allocated by populations still needed to improve. The mention of “Accelerating talented professionals in rehabilitation” and other pertinent topics in the National People's Congress and the Chinese People's Political Consultative Conference in 2017, as well as the regulations on disability prevention and rehabilitation promulgated by the State Council, may be responsible for the Global Moran's I index's decline and stabilization after it peaked in 2017. The impact of major conferences or policies in the field of health on the spatial autocorrelation of human resource development in rehabilitation institutions in China may be a process of fluctuation and narrowing. The specific impact changes need further studies.Therefore, the effectiveness of health policies, especially those related to the construction of rehabilitation institutions and the training of rehabilitation specialists, should be paid more attention to. The continuous role of such policies will affect the spatial distribution of staff in rehabilitation institutions.Due to the external interference factors, such as the social economy and natural environment, there will be varying degrees of spatial heterogeneity when a large area is selected for research , 30. Bas(1) The human resources of rehabilitation institutions had a certain spatial spillover effect. Under the interaction of adjacent provinces, the investment in human resources of this province was affected by the personnel flow of neighboring provinces to a certain extent, and this led to a continuous “depressions” effect in Heilongjiang from 2016 to 2019 . This co(2) Due to its vast territory, sparsely populated area, and relatively backward economic development compared with other regions, it is difficult for the provinces in western China to gain adequate attraction for rehabilitation professionals. On this basis, the investment and attention of local governments in the rehabilitation industry will decrease, which will result in further specialist scarcity and ultimately form a destructive cycle. This explains why those provinces in western China mostly showed Low–Low aggregation.Compared with other medical and health institutions and the Centers for Disease Control and Prevention in China, which have clear provisions on their staffing ratio, there is a lack of regulations regarding the number and proportion of staff in rehabilitation institutions in China. The lack of regulations may lead to some errors when studying the allocation of rehabilitation staff in various provinces. Establishing a reasonable SRID index is a key and effective step to improve the maldistribution of human resources of rehabilitation institutions in China.The result of spatial clustering in this study was quite different from other scholars' research results of human resources allocation , which might be caused by different research objects . PreviouThe unique study results also suggest that systematic and multi-factor comprehensive consideration should be taken into account while making a research design processing and in the analysis of resource allocation so as to reasonably define the scope of the target population and promote the formulation of reasonable and effective policies.The result of LISA showed too many NG types in most provinces. One of the possible reason for is that the extremely significant aggregation in very few regions/provinces obviously covers up the aggregation in other regions. More microscopic research needs to study further like central region in China.This study focused more on the gaps between different provinces. Actually, the gaps within provinces also exist, and the degree of economic development in provinces may show different maldistribution. On the other hand, the duration of the study started from 2016 to 2019 due to the different statistical indicators in the CSYWPDs before 2016 and the pandemic of COVID-19 in 2020, which led to a short study period. Future research should explore the gaps within provinces and a long-term analysis on regional distribution of human resources of rehabilitation institutions.Spatial statistical analysis can intuitively and continuously analyze agglomeration and changes caused by certain factors at different time nodes. There are still several inequities regarding allocating human resources in rehabilitation institutions in China. The most prominent one is that PP was relatively low, and rehabilitation specialists were strongly demanded in most provinces. In order to ensure that the rehabilitation work for the disabled in China is in line with international standards and develops smoothly, the following recommendations were put forward for reference : (1) To effectively analyze the main rehabilitation needs of the disabled in China, a long-term plan for the training, education, certification, and use of rehabilitation professionals should be formulated; (2) A reasonable “SRID” index of rehabilitation institutions that meets the specific conditions of each province, which could provide guarantees and references to evaluate the overall situation and formulate relevant health policies, should be developed; (3) A reasonable target population range with resource demands for improving the effectiveness of policy implementation should be considered.http://www.zgtjcbs.com; http://www.stats.gov.cn/tjsj/ndsj/2019/indexch.htm.Publicly available datasets were analyzed in this study. This data can be found at: CC contributed to material preparation, data analysis, and the first draft of the manuscript. TC contributed to data collection, the conception of the study, and modification opinions. NZ was responsible for polishing the article. SD contributed significantly to analysis and manuscript preparation, helped perform the analysis with constructive discussions, and polish the article to make it more readable. CC, TC, NZ, and SD contributed to the study's conception and design and commented on previous versions of the manuscript. All authors read and approved the final manuscript.This research was funded by the National Key Research and Development Plan of China (Grant No. 2020YFC2006000). The funders had no role in the study design, data collection and analysis, decision to publish, and preparation of the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Although nearly one-third of the world’s disease burden requires surgical care, only a small proportion of digital health applications are directly used in the surgical field. In the coming decades, the application of augmented reality (AR) with a new generation of optical-see-through head-mounted displays (OST-HMDs) like the HoloLens (Microsoft Corp) has the potential to bring digital health into the surgical field. However, for the application to be performed on a living person, proof of performance must first be provided due to regulatory requirements. In this regard, cadaver studies could provide initial evidence.The goal of the research was to develop an open-source system for AR-based surgery on human cadavers using freely available technologies.We tested our system using an easy-to-understand scenario in which fractured zygomatic arches of the face had to be repositioned with visual and auditory feedback to the investigators using a HoloLens. Results were verified with postoperative imaging and assessed in a blinded fashion by 2 investigators. The developed system and scenario were qualitatively evaluated by consensus interview and individual questionnaires.The development and implementation of our system was feasible and could be realized in the course of a cadaver study. The AR system was found helpful by the investigators for spatial perception in addition to the combination of visual as well as auditory feedback. The surgical end point could be determined metrically as well as by assessment.The development and application of an AR-based surgical system using freely available technologies to perform OST-HMD–guided surgical procedures in cadavers is feasible. Cadaver studies are suitable for OST-HMD–guided interventions to measure a surgical end point and provide an initial data foundation for future clinical trials. The availability of free systems for researchers could be helpful for a possible translation process from digital health to AR-based surgery using OST-HMDs in the operating theater via cadaver studies. Health care is increasingly supported by digital technologies . Almost Further technical development has made optical-see through head-mounted displays (OST-HMDs) such as the HoloLens (Microsoft Corp) commercially viable with broad use in the industry . Health By feeding back relevant information to the surgeon during surgical tasks based on preoperative or intraoperative medical imaging data or AI-based guided models, AR with or without image-guided surgery (IGS) could overcome one of the main problems of surgical procedures, which is that they mainly rely on the surgeon’s spatial awareness or haptic perception in the surgical field ,5. AR itAR applications have been used since the mid-1990s, mainly for surgical procedures on rigid tissue in the head and neck region. Examples of applications in the operating theater are orthognathic surgery, oncology including parotid surgery, and traumatology. Anatomical and pathological structures, drilling and implant position, resection margins, and reconstructive planning are visualized using different AR technologies ,11. SimiDue to the underlying technology with external monitors, however, many of these deployed systems result in a dissociation between the perceptual site and the operational field ,10. HMDsOn the road to widespread use of this rapidly developing technology, proof of performance is essential, especially in the regulatory context. Cadaveric studies have long provided a contribution to demonstrating the performance of new medical technologies and are considered a prestudy proof of performance prior to clinical trials . HoweverIn order to enhance the development of digital health in surgery, we aimed to develop an AR- and OST-HMD–based system for a cadaveric study using free technologies to make it available and adoptable for research in various experimental surgical scenarios as proof of performance. Furthermore, we wanted to investigate if cadaver studies using this system would be suitable for testing system feasibility, applicability in a surgical task that relies primarily on spatial and haptic perception, and evaluability of its surgical end point.We chose a simple and understandable AR scenario on fresh cadaver heads using a HoloLens, where the surgeon had to reduce a fractured zygomatic arch, a common injury of the human face.The purpose of our study was to develop an AR-based system for IGS to be used in a surgical environment with human cadavers. The aim was to augment the surgeon’s spatial perception with 3D models based on previous medical imaging by overlaying them on the surgical field using AR. This overlay is intended to be adaptive by adjusting to the current position of the cadaver and surgical instruments and to allow interaction between both. Three essential feedback functions should be provided here: feedback of the proximity of the surgical instrument to surgical target structures by means of a visual signal, an auditory signal, and a visual representation of the movement of the surgical instrument. The graphical user interface should allow intuitive selection of the different cases with specific models and different functions by gestures via AR-based buttons. Furthermore, all described functionalities should also be usable with voice commands to enable hands-free working.Overall, the system should be easily adaptable to different surgical scenarios, cost-efficient, and easily replicable by third parties, allowing it to be universally applicable as proof of performance for OST-HMDs in surgery on cadavers.We aimed to achieve our requirements by using the commercially available HoloLens 1 as one of the state-of-the-art and most broadly used OST-HMDs combined with the camera-based tracking system Vuforia . Our software prototype was developed using the C# programming language with the popular game engine Unity 2018.4.13f LTS (Unity Technologies) and the Mixed Reality Toolkit  for rapid prototyping. Our software prototype was then developed into a prerelease candidate of an open-source software as part of a master’s thesis in computer science .Based on medical imaging data, 3D models were created for the cadavers and surgical instruments a. In ordA graphical user interface was developed for the AR software to make the virtual anatomical models of the respective cadavers selectable via AR-based buttons and to adjust the software . It had When a virtual model was selected, it was superimposed on the real cadaver head by continuous tracking d. The suThis article does not include studies with live human participants or animals. Approval by the ethics committee of the University Hospital RWTH Aachen  has been granted. The investigators agreed to participate in the study.Ten fresh cadaver heads were randomly selected. The initial condition of the facial skeleton was first scanned with cone beam computed tomography . To ensure a consistent method, a metal angle was attached to the bone of the forehead of each cadaver to attach the tracking mount a and 2b Based on the acquired medical imaging data, 3D models were created for all cadaver heads with the initial situation and fractured zygomatic arches. Both models were registered using the best fit alignment feature of Geomagic Studio 2013 (3D Systems Inc) and loaded into our software. In addition, a Stromeyer hook, a surgical instrument routinely used to reduce zygomatic arch fractures, was digitized and loaded into our software. For tracking, mounts were then 3D printed for fixation on the cadaver heads and on the Stromeyer hook d.The cadaver heads were randomly assigned to the investigators (a resident and a senior surgeon). One zygomatic arch side of each head was randomly selected (based on a random number generator) for reduction by the conventional method and the opposite side by the AR-based method. Before reduction, the investigators were able to view the CBCT imaging data with the fractured situation on a computer. The conventional reduction was performed with the Stromeyer hook through a percutaneous incision and was based only on haptic perception. The AR-based reduction was performed identically, with the addition of a registered virtual model of the Stromeyer hook and a registered virtual model of the intact zygomatic arch of the corresponding cadaver displayed on the HoloLens. The aforementioned functionalities of feedback through color transition, virtual drawing, and audio signals provided the investigators with additional visual and auditory perception c and 4d.Based on postoperative imaging, 3D models of the cadaver heads were created and registered with the corresponding preoperative and initial situation using Geomagic Studio 2013. The zygomatic arch was defined as the region from the temporal origin of the zygomatic process to a straight vertical extension line at the posterior margin of the frontosphenoid process of the zygoma and converted to separate models. The deviation of the different models was then compared . The initial nonfractured model was used as a reference and compared to the fractured model and subsequently to the reduced model . The resFinally, reduction quality was classified into 4 levels based on postoperative imaging by 2 noninvestigators in a consensus and blinded fashion according to Yakomoto et al : poor foThe AR software was assessed using the System Usability Scale (SUS) . AfterwaThe R programming language  was used for statistical analysis. Results were expressed as mean and standard deviation. The 95% confidence intervals were calculated by bootstrapping with 1000 replications .Within the quantitative reduction measurement between fractured and reduced zygomatic arches, our test scenario showed a mean reduction of 0.78 mm (95% CI 0.37-1.29 mm) for the conventional method and 0.52 mm (95% CI 0.23-0.77 mm) for the AR-based method a. The meBased on consensus interviews with both investigators, the vertical field of view (FOV) was considered small and tracking mounts could interfere in certain surgical scenarios. When using the HoloLens 1, it was noted that an incorrect fit on the head could also lead to an error in superimposition between virtual and real objects. In this context, the simple half-cube for holographic verification was perceived as helpful for evaluation. Visualization of the fractured condition was preferred over the nonfractured one for navigation.In addition, an individual Likert questionnaire was performed . Both inIn our study, we demonstrated that it is possible to develop an adaptable and usable AR-based system with OST-HMDs and image-guided capacities for surgical interventions by combining freely available technologies and evaluating them in a test scenario on human cadavers. This system can be adopted by researchers worldwide and adapted to their own surgical scenarios. The implementation will require a HoloLens or Unity-compatible OST-HMD, the ability to capture 3D medical imaging data, and a 3D printer to produce suitable mounts for the cadaver and surgical equipment. The software and models of the 3D mounts are freely available under an open-source license.However, the presented system still has shortcomings. When using HoloLens, we have found that an incorrect fit on the head leads to a positioning error between the eyes and the semitransparent display, causing perceptual errors. Only with the correct fit were both real and virtual objects correctly superimposed. For this reason, the simple half-cube we have developed for holographic verification can be used for evaluating the superimposition between real and virtual objects to represent possible errors in the fit of an OST-HMD or, additionally, errors in tracking by user-verifiable reference surfaces c. The FOAlthough the tracking mount was not found to be a disturbance by the investigators, it could become a potential concern during surgical procedures where space is limited or could lead to tracking errors because the tracking mount is obscured. One solution would be a mount-free or electronic tracking method to avoid disturbing surgeons in such situations .Previous studies that evaluated image-based tracking using Vuforia and a HoloLens indicated a position error of 1.74 to 1.94 mm ,30. Our In our scenario, it was possible to visualize both the fractured and nonfractured situation, as the healthy bone condition can often be reconstructed with little effort by mirroring the nonfractured side, especially for the face . Since iOur system provided visual and auditory feedback depending on the distance of the surgical instrument working area and intended reduction situation of the bone. This was realized visually via a color change of the virtual zygomatic arch model as well as via the possibility of graphical representation of the movement path of the surgical instrument tip. The drawing function can be used to show the internal contour of bones—in our case, the contour of the fractured bone. If a fracture offset is present, it would be represented by an offset of the drawing line d. To ourIt has already been shown that studies with OST-HMDs on cadavers are suitable to measure the difference between the planning of drill holes, placement of screws, or performance of osteotomies and the actual performance -22. Our Studies on fresh cadavers, however, cannot determine clinical outcomes such as pain, patient-guided range of motion, dysfunction, or other clinical parameters. Nevertheless, cadaveric studies can be used to provide a data basis for subsequent clinical study planning. The technical system can be evaluated and tested. The developed AR system did not result in a large temporal difference from the conventional method in our scenario. It is important to measure duration as an end point, as surgery time is an important quality indicator. Prolonged surgery durations lead to a greater number of complications for the patient  and incrOverall, the number of studies with application of AR-based surgery with OST-HMDs in cadaveric studies is small -22. In cThe development and application of an AR-based surgical system using freely available technologies to perform OST-HMD–guided surgical procedures in cadavers is feasible, but our presented open-source prototype should be further developed. Cadaver studies are suitable for OST-HMD–guided interventions to measure a surgical end point and provide an initial data foundation for future clinical trials. In this regard, it has been shown in our scenario that the effect of the AR-based approach could be more likely to make a difference in residents. This should be considered when planning future trials. The availability of free systems for researchers could be helpful for a possible translation process from digital health to AR-based surgery using OST-HMDs in the operating theater via cadaver studies.


Atmospheric rivers (ARs) are efficient mechanisms for transporting atmospheric moisture from low latitudes to the Antarctic Ice Sheet (AIS). While AR events occur infrequently, they can lead to extreme precipitation and surface melt events on the AIS. Here we estimate the contribution of ARs to total Antarctic precipitation, by combining precipitation from atmospheric reanalyses and a polar‐specific AR detection algorithm. We show that ARs contribute substantially to Antarctic precipitation, especially in East Antarctica at elevations below 3,000 m. ARs contribute substantially to year‐to‐year variability in Antarctic precipitation. Our results highlight that ARs are an important component for understanding present and future Antarctic mass balance trends and variability. Atmospheric rivers (ARs) contribute around 13% ± 3% of the total Antarctic Ice Sheet (AIS) precipitation each yearThe relative contribution of ARs to precipitation is most substantial in East AntarcticaARs explain a large fraction (35%) of interannual variability in AIS precipitation We selected this 24 ± 6 hr period after careful analysis of precipitation rates in MERRA‐2 during and after AR events. For this analysis, we used an hourly version of the AR detection algorithm . While the relative increase initially increases steeply , the relative increase between each 3 hr increase quickly lowers, and is lower than 5% after 18 hr. This remaining small increase with a later cut‐off time is to be expected, and likely due to the residual AR‐related moisture being incorporated in mesoscale cyclogenesis over the AIS, the impact of a new AR as part of a series of ARs passing by the same location, and/or the general occurrence of AIS precipitation occurring outside the footprint of the detected ARs.3−1, equivalent to a 13% ± 3% of total precipitation . The relative importance of AR precipitation is slightly higher on the grounded ice sheet (14%) than on ice shelves (11%), and higher on East Antarctica (16%) than on West Antarctica (9%) and the Antarctic Peninsula (10%). These results imply that the relative impact of ARs on precipitation is at least an order of magnitude higher than their frequency on the AIS, which does not exceed 1%–1.5%  between interannual variations of ice sheet integrated AR precipitation and its relative contribution to total AIS precipitation , indicating that ARs can explain more than a third of the interannual variability in total AIS precipitation, almost three times as much as ARs contribute to mean precipitation. Additionally, we find that the relative contribution of ARs to total AIS precipitation displays a small but discernible seasonal cycle (not shown), with a peak in winter and spring (>13.5%) and a relative minimum (<12.5%) in summer (December–February). Considering the substantial interannual variations, this seasonal cycle is nonetheless non‐significant.Interannual variations in AR precipitation on the AIS are substantial, which is illustrated by the high (25%) ratio between the 1980–2020 AR precipitation standard deviation and mean, in comparison to the 5% ratio for total precipitation. This is further confirmed by the strong correlation . AR precipitation, on the other hand, shows a clear and statistically significant upward trend . The opposite long‐term trends imply that the relative contribution of ARs to AIS precipitation has increased toward the later years of the time period , both for the grounded ice sheet and ice shelves. In 2009 and 2011, when multiple ARs hit the Dronning Maud Land area  correlated with the frequency of ARs on Antarctica  correlation between AR precipitation and the annual average maximum IVT value in ARs on the AIS  scale, but is relatively constant throughout the seasons and across elevation. Our results provide a 41‐year long, spatially continuous record of AR precipitation on Antarctica. Given the substantial interannual variability of AR frequency and their precipitation impacts, our results aid to provide a broader context to short‐term, limited‐area contribution of ARs to annual precipitation on Antarctica . This likely leads to an underestimation of the highest precipitation rates, such as those associated with ARs, and thus an undercatch of the total precipitation assigned to an AR. Secondly, our assumed spatiotemporal footprint of an AR on precipitation likely underestimates its real footprint. We only assign precipitation directly underneath an AR to that system, while in reality, the precipitation field of an AR might be more expansive than that of the AR itself. The 24‐hr time window after AR passage we use (and justify) might miss precipitation that persists for more than 24 hr after the passage of strong AR systems (Wille et al., Current AR impacts in most regions of Antarctica are focused on snowfall, and thus ARs contribute positively to Antarctic surface mass balance. However, larger contributions of ARs to snowfall in East Antarctica compared to West Antarctica suggest that current AR impacts vary regionally. One hypothesis for this discrepancy is that West Antarctic ARs are less persistent, less meridionally expansive, and/or more of the “windy and warm” rather than “wet” type (Gonzales et al., Figure S1Click here for additional data file.