CYP1A1 MspI polymorphism and the risk of HNC in an updated meta-analysis. The PubMed/MEDLINE, Web of Science, Cochrane Library, and Scopus databases were searched until March 31, 2021, without any restrictions. Odds ratios (ORs) and 95% confidence intervals (CIs) were applied to assess a relationship between CYP1A1 MspI polymorphism and the HNC risk based on five applied genetic models by RevMan 5.3 software. Other analyses  were performed by CMA 2.0 software. Trial sequential analysis (TSA) was done by TSA software (version 0.9.5.10 beta). Among the databases and other sources, 501 recorded were identified that at last, 29 studies were obtained for the analysis. The pooled ORs were 1.28 , 1.68 , 1.24 , 1.26 , and 1.66  for allelic, homozygous, heterozygous, recessive, and dominant models, respectively. Therefore, the m2 allele and m1/m2 and m2/m2 genotypes had significantly increased risks in HNC patients. With regards to stable results and enough samples, the findings of the present meta-analysis recommended that there was an association between CYP1A1 MspI polymorphism and the HNC risk.The studies recommended the relationship between lots of polymorphisms with the head and neck cancers (HNCs) risk. Herein, we reported the association between the  Men are significantly more affected by this type of cancer than women with a ratio of 2: 1 to 4: 1 and the prevalence of important anatomical sites of HNC  varies in different parts of the world4. HNC's current and future estimated load is shifting to less developed areas that may not have the equipment to cope with this increased load and this requires immediate attention by policymakers through the implementation of effective cancer control policies with population-based interventions2. There are many factors that can increase the incidence or prevalence of HNC, including the relative distribution of major risk factors such as alcohol consumption, tobacco, and smoking5. Genetic elements have also been implicated in the pathogenesis of this cancer. In support of this statement, several recent meta-analyses have confirmed the relationship of various polymorphisms with the risk of HNC11. Two reviews confirmed the relationship between several polymorphisms with the risk of HNC13. Therefore, HNCs are a complex multifactorial disorder that includes genetic, lifestyle, and environmental factors15. Cytochrome P450 (CYP) enzymes perform a major role in the metabolic activation of polycyclic aromatic hydrocarbons (PAHs) to epoxide intermediates, suggesting a link between PAHs, the CYP pathway, and cancer development that cytochrome P450 1A1 (CYP1A1) is believed to be the most important enzyme in this link16 and CYP1A1, as a drug-metabolizing enzyme, is among the main enzymes imported in the processing of tobacco-related carcinogens17. A studied polymorphism in the CYP1A1 gene  has been shown to be related to the cancer risk, known as CYP1A1 MspI polymorphism (CYP1A1*2A)18 that CYP1A1 MspI is a T → C transition placed downstream of exon 7, in 3′ noncoding region19. This polymorphism may change the gene expression level or the messenger RNA stability due to highly induced enzymatic activity20. Seven meta-analyses checked the relationship between CYP1A1 MspI polymorphism and the risk of HNC including two case–control studies21, twelve in Asians with oral cancer22, seven23, thirty-two24, twelve including oral cancer25, twelve26, and twelve27. The meta-analysis He et al.24, although had more studies than other meta-analyses, focused on several types of cancer at the same time and didn’t provide information on sensitivity analysis, meta-regression, trial sequential analysis (TSA), and publication bias for HNC. In comparison with our study and other meta-analyses, this meta-analysis included thyroid cancer and different sites of head and neck as HNC, apart from that oral cavity, larynx, and pharynx. In comparison with the meta-analysis of He et al.24, we excluded studies that did not have a sufficient number of cases in their groups or their control groups had a deviation from Hardy–Weinberg equilibrium (HWE), because reducing the bias across the studies. Therefore, we aimed to evaluate the connection between the polymorphism of CYP1A1 MspI and the risk of HNC with twenty-nine studies in a meta-analysis, meta-regression, and TSA.Head and neck cancer (HNC) affects more than 650,000 cases and 330,000 deaths each year28. The PICO  question was: Is CYP1A1 MspI polymorphism related to the HNC susceptibility comparing the prevalence of its alleles and genotypes in HNC patients in comparison with controls according to five genetic models?This present study was designed by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocolsA systematic search was comprehensively used in PubMed/MEDLINE, Web of Science, Cochrane Library, and Scopus databases until March 31, 2021, without any restrictions. The used search terms were: (“cytochrome P4501A1” or “CYP1A1” or “AHH” or “aryl hydrocarbon hydroxylase”) and  and . An independent review of titles and abstracts was conducted by two authors (H.M. and M.S.). A lack of consensus was resolved by a conversation with a third author (M.M.R). We manually checked other electronic sources for relevant studies and also the references of all subject-related studies that met the criteria so that no study was missed.CYP1A1 MspI polymorphism and the HNC susceptibility; (2) HNC was diagnosed by pathological or histological examinations; (3) sufficient data calculating the allele or genotype frequencies of CYP1A1 MspI polymorphism; (4) studies without a deviation from HWE in the control group or studies that HWE could not be computed ; (5) Studies having 100 or more than 100 cases in both groups (case and control groups). Exclusion criteria were: (1) duplicate publications; (2) meta-analyses, reviews, letters to the editor, book chapters, conference papers, book chapters; (3) studies in the absence of control group; (4) studies reporting other polymorphisms of CYP1A1; and (5) studies reporting the CYP1A1 expression; (5) Studies with less than 100 cases in one or two groups; and (6) family-based studies. Among duplicate publications, we selected one with the newest date. An independent review of full-texts was conducted by two reviewers (H.R.M. and M.S.) and the disagreement was resolved by discussion between both reviewers.Inclusion criteria were: (1) studies with a case–control design and reporting the association between The data of the involved studies were extracted independently by two reviewers (H.M. and M.S.) to retrieve the necessary information. In case of discrepancy between the data of the two reviewers, a new review was performed by other reviewers (M.M.R and F.R).29. The NOS included a maximum of nine scores for the least risk of bias in three domains: I) selection of study groups (four scores); II) comparability of groups (two scores); and III) ascertainment of exposure (three scores) for case–control studies30. Two reviewers (H.M. and M.S.) independently evaluated the quality of the included studies by scoring them according to a set of pre-established criteria and discrepancies were resolved by a short discussion.The quality evaluation was performed according to a questionnaire from the Newcastle–Ottawa scale (NOS)CYP1A1 MspI and the cancer risk. Five applied genetic models for CYP1A1 MspI polymorphism were , homozygous (m2/m2 vs. m1/m1), heterozygous (m1/m2 vs. m1/m1), recessive (m2/m2 + m1/m2 vs. m1/m1), and dominant (m2/m2 vs. m1/m1 + m1/m2) models). To assess heterogeneity, a Chi-square-based Q test and inconsistency index I2 were applied32 that a P-value > 0.10 (I2 < 50%) presented a lack of heterogeneity and so we used fixed-effects model33 and if there was heterogeneity, the pooled results estimated by the random-effects model34.Both odds ratio (OR) and 95% confidence interval (CI) were used to evaluate an association between the polymorphism of Subgroup analysis is a method of analysis that involves dividing all participating data into smaller subsets based on a common feature and is often used to compare them and to examine the effects of different factors on the results. We divided the initial results based on ethnicity, control source, and tumor type.35. We assessed the effect of publication year and sample size on the effect size.Meta-regression is a quantitative method performed in meta-analysis to estimate the effect of moderators on the effect size of the study applying regression-based techniquesThere were two sensitivity analyses containing “one-study-removed” and cumulative analysis” to evaluate the stability/consistency of pooled results.36. Both Begg’s37 and Egger’s38 tests were used for the diagnosis of asymmetry of these plots. Asymmetry can be a reason for bias in studies that in the state, P-values (two-sided) < 0.05 for the tests.Funnel plots are visual tools for evaluating the types of biases in meta-analyses and are designed to examine whether publication bias can affect the reliability of estimatesP-values (two-sided) < 0.05 was as a significant index. The results of forest plot analyses were extracted by Review Manager 5.3 (RevMan 5.3) software and other analyses by Comprehensive Meta-Analysis version 2.0 (CMA 2.0) software.The 39 in the meta-analysis using TSA software (version 0.9.5.10 beta)  to reduce these statistical errors40. The required information size (RIS) was calculated when an alpha risk of 5%, a beta risk of 20%, and a two-sided boundary type were used. While the Z-curve reached the RIS line or monitoring the boundary line or futility area, it illustrated that enough samples are involved in the studies, and therefore their results were valid. Otherwise, the value of information was not great enough, and additional studies were needed.We used TSA due to false-positive or negative conclusionAll methods were performed in accordance with the relevant guidelines and regulations.CYP1A1, two reported duplicate publications, one family-based study, one had no sufficient data, one reported oral precancerous cases, twelve studies reported less than 100 cases in one or two groups (case and control groups), and seven meta-analyses). After that, 34 studies73 were included systematic review and we deleted 5 studies72 with a deviation from HWE in their control groups. Finally, 29 studies were entered into the analysis.Among the databases and other sources, 501 recorded were identified  for allelic, 1.68  for homozygous, 1.24  for heterozygous, 1.26  for recessive, and 1.66  for dominant models. The m2 allele and m1/m2 and m2/m2 genotypes had significantly an elevated risk in HNC patients.Figures CYP1A1 MspI polymorphism and HNC risk based on five models , two models ), and two models  were statistically significant for Asian, Caucasian, and mixed ethnicities, respectively, that in contrast with Asian and Caucasian ethnicities, there was a decreased risk of m2 allele and m1/m2 genotype in mixed ethnicity. For the control source, the association was statistically significant in four models  for hospital-based controls and three models (heterozygous and recessive) for population-based controls. For tumor type, the association in four models  for oral cancer, three models  for laryngeal cancer, and three models  for pharyngeal cancer was statistically significant.The subgroup analysis was performed on the ethnicity, the control source, and the tumor type Table . The resCYP1A1 MspI polymorphism and the risk of HNC based on the genetic models. Both Egger’s and Begg’s tests were: . The P-values > 0.05 were for both tests that determined lack of any publication bias across the studies, exception for Egger’s test in dominant model (P < 0.05) that showed the publication bias across the studies in this model.Figure CYP1A1 MspI polymorphism was related to the HNC risk with enough samples and reliable results that we selected the graphs for four models because of the better quality of the graphs  of the allelic, homozygous, heterozygous, recessive, and dominant models reached the RIS line , revealing that the phs Fig. .Figure 8The sensitivity analyses including “one-study-removed” Fig.  and “cumCYP1A1 MspI polymorphism (Table CYP1A1 MspI polymorphism (P < 0.05). Increasing the sample size, the risk of HNC significantly increased (a direct correlation).A meta-regression analysis based on the publication year and the sample size were carried out on the relationship between the HNC risk and sm Table . The ana74. Our meta-analysis reported the association of one of the polymorphisms (CYP1A1 MspI) in these genes with the HNC susceptibility. The results were stable and showed elevated risks of m2 allele and m2/m2 and m1/m2 genotypes in HNC patients with enough samples that the results were under the influence of the ethnicity, the tumor type, and the control source. In addition, the sample size, the tumor type, and the ethnicity could be confounding factors on the results.A recent systematic review reported that 242 genes have associated with the risk of HNCGSTs) such as GSTT1, GSTM1, and CYP1A1 MspI genotypes, suggesting that cross-linking between these genes may modulate nasopharyngeal cancer susceptibility, with similar results reported in HNCs75. As the results of one study showed, CYP1A1 polymorphisms alone were not related to an increased risk of oral cancer and the moderate risk for oral cancer was combining this polymorphism with GST polymorphisms69. Cha et al.76 showed the role of combined genotypes of CYP1A1 m2/m2 and GSTM1 null in the oral cancer risk. Cyp1A1 MspI polymorphism in lung cancer was associated with PAH-DNA adduct levels77 and the frequency of p53 gene mutations78. Smokers had the significant elevated risk  of nasopharyngeal cancer among individuals carrying CYP1A1 MspI m2/m2 + m1/m2 genotype71.A 5.71-fold risk of nasopharyngeal cancer has been reported in cases carrying glutathione-S-transferases  appeared as a significant moderator in cases with variant genotypes of CYP1A1 in India69. Sharma et al.65 expressed that CYP1A1 gene haplotype  frequency distribution in HNC patients was significantly higher than controls. Therefore, it is important to consider the haplotype and the combined impacts of genetic and environmental factors when examining the genetic risk to complex illnesses such as HNC65.One study in Northeast India found that the susceptibility to HNC related to tobacco and alcohol consumption is modulated by CYP1A1 polymorphisms and HNCs in Indians may be due to ethnic differences in culture, linguistics, and diets in this population, or they may be because of a difference in the sample size of the studies63. As our meta-analysis confirmed that the sample size was a confounding factor on the association and increasing the sample size, OR increased.The discrepancies between results of the association between 79 reported that the association between CYP1A1 polymorphisms and the risk of HNC could be affected by tumor type as that they observe an elevated risk of laryngeal and pharyngeal cancers, but no for oral cancer. Another study70 showed that the m2/m2 genotype of CYP1A1 MspI polymorphism had a significantly elevated risk in oral cancer patients, but there was no significant relationship between this polymorphism and pharyngeal and laryngeal cancers that one review80 confirmed it. Also, Sam et al.63 showed the association between m1/m2 genotype had just significant risk in laryngeal and pharyngeal cancers, not oral cancer. In our meta-analysis, the m1/m2 genotype had just a significant association with pharyngeal cancer and m2/m2 just in oral and laryngeal cancers.Wang et al.27 reported the association between CYP1A1 MspI polymorphism and the risk of HNCs. Two meta-analyses25 illustrated that the CYP1A1 MspI polymorphism may be associated with oral cancer susceptibility in Asians as well as Xie et al.81 in a stratified analysis by ethnicity, showed significant evidence of the association of CYP1A1 MspI polymorphism with the HNC risk in Asian ethnicity, but not mixed and Caucasian ethnicities. These results showed the impact of ethnicity on the relationship between CYP1A1 MspI polymorphism and the HNC risk as the meta-analysis of He et al.24 and our meta-analysis reported. In addition, our meta-analysis showed an association between other cancers , both in Asians and in other ethnicities (Caucasian and mixed ethnicities). Some studies84 and our meta-analysis to follow them, classified Indians in Caucasian ethnicity and some other studies86 as Asians, but based other studies88, Indians include several ethnicities (mixed). One possible difference between the results of studies can be due to the different classification of the ethnicity for each region. Therefore, it should be noted that there is a need for a comprehensive classification to select the type of ethnicity of each country or region in the future so that the results of meta-analyzes based on the ethnicity be more homogeneous. In addition, in the meta-analyzes mentioned27, the number of studies was different and this could be another reason for the difference between their results. So, more studies are needed in different areas in the world to reduce this difference in results between studies. As the results of different studies and their contradictions showed, the relationship between this polymorphism and HNC risk is influenced by various factors, and paying attention to the effective factors in future studies can provide a way to find more dominant factors. As a result, treatment of these patients and as a result of increasing their survival can be done more easily and under more effective and better conditions.Seven meta-analysesApart from several strengths , the present meta-analysis also had some limitations as (1) High heterogeneity between the studies. (2) Few numbers of studies in Asian and mixed ethnicities. (3) The impact of risk factors on the results with different distributions in included studies. (4) We just included published studies.CYP1A1 MspI polymorphism and the HNC susceptibility with enough samples and stable results. The ethnicity, the tumor type, the control source, and the sample size were significant risk factors for the results. Therefore, pay attention to these factors can be important in relation to the association of CYP1A1 MspI polymorphism and the HNC risk in future studies. In addition, well-designed studies with large samples in various areas of the world with precise matching criteria are required to reveal the present meta-analysis conclusions.The findings of the present meta-analysis recommended the association between


Asthma is the most common respiratory disease among children, while atopic diseases such as atopic dermatitis affect about 20% of infants under 2 years of age. Studies suggested that these conditions might be related to prenatal depression or anxiety. This study aimed to explore the association between prenatal mental disorders and childhood asthma or atopic disease in a systematic review and meta-analysis.I2 > 50% and Q-test P < 0.10.PubMed, Embase, and the Cochrane Library were searched up to May 2020. The primary outcome was childhood asthma and childhood atopic dermatitis. Random-effects models were used because of high heterogeneity indicated by n = 6 studies; ES = 1.146, 95%CI: 1.054–1.245, P = 0.001; I2 = 93.5%, Pheterogeneity < 0.001) whereas no significant association was found for childhood atopic dermatitis . Childhood asthma seems to be related more to depression  and anxiety/depression .A total of 598 studies were initially identified, but nine studies met the inclusion criteria. Prenatal mental disorder was associated with childhood asthma (This meta-analysis demonstrated that prenatal mental disorders increase the risk of childhood asthma. We limited the included samples to pregnant women to investigate the association between prenatal psychological factors and offspring’s physical health. Future studies should include large high-quality cohort studies to investigate the behavioral, environmental, and genetic causes for this association.The online version contains supplementary material available at 10.1186/s12884-021-03909-z. In terms of the developmental origins of health and disease, there is evidence that adverse early-life exposure associated with maternal psychiatric diseases can alter the immune system and exacerbate the risk of asthma and atopic diseases such as atopic dermatitis (AD) –4. AsthmA meta-analysis of 41 studies carried out in 2019 revealed a significant influence of parental  mental diseases and childhood asthma but no association with AD . In the Therefore, it is still unclear whether childhood asthma or AD is related to maternal mental diseases. We sought to undertake an updated meta-analysis and systematic review of all studies investigating the prenatal impact of anxiety and depression on childhood asthma and AD.The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were implemented for this systematic review and meta-analysis . We searWe included observational studies that examined the associations between prenatal mental diseases (depression and anxiety) and asthma and AD, with language limited to English. The participants were children and their biological mothers who undertook an intentional study with medical records access. The analysis was based on mothers with prenatal anxiety or depression (exposure) vs. mothers without prenatal anxiety or depression (non-exposure).For this systematic review and meta-analysis, we searched PubMed, Embase, and the Cochrane Library for studies published up to May 2020 with language and article type restriction. Supplementary Table The data were extracted independently by two investigators. The study characteristics , treatment parameters  from each included study unless we determined any additional variables in the causal relationship between exposure and outcome. If aOR were not available, the crude ORs were extracted. When studies showed multiple exposures with multiple impact sizes, we reported only those exposures that the investigator considered the most severe and chronic. When a study reported multiple results separately, we extracted two results for different analyses. When a study reported only analyses of different asthma types, such as early or late-onset transient asthma, we treated the effect size as two independent outcomes. When a single study was available, the effect sizes of that study were presented.We assessed the cohort or case–control studies using the Newcastle–Ottawa Scale (NOS) . Quality2 index to calculate statistical heterogeneity, for which high heterogeneity was defined as I2 > 50% and P < 0.10 in the Q-test [STATA SE 14.0  was used for all analyses. The studies were grouped by types of outcomes. The comparison between results was employed effect and corresponding 95% confidence interval (CI) for each group. We used Cochran’s Q test and Ie Q-test . A randoe Q-test .n = 302), Embase (n = 265), and the Cochrane Library (n = 31). After removing the duplicates, 432 articles were examined. Ten articles were excluded because of being notes/reports, 109 articles were excluded because they were conference abstracts, 25 articles were excluded because of being reviews, and 15 articles were excluded because of the language. Then, 273 articles were left for full-text screening and 264 were excluded because of being not accessible (n = 10), study aim/design (n = 54), population (n = 100), outcome (n = 28), intervention (n = 63), and animal (n = 9). No additional records were identified through other sources. Hence, nine observational studies entered our final model [Figure al model , 21–26.FTable P = 0.001; I2 = 93.5%, Pheterogeneity < 0.001)  , 24, 25 2 = 78.5%, Pheterogeneity < 0.001)  , 25, 26 01) Fig. .Table 3TP = 0.746). Another study examined prenatal depression and childhood asthma [P = 0.002). Four studies considered prenatal depression or anxiety [P = 0.003; I2 = 95.3%, Pheterogeneity < 0.001)  that showed a borderline possible association between prenatal mental disorder and childhood asthma, whereas four retrospective studies [P = 0.003; I2 = 95.3, Pheterogeneity < 0.001) , but two studies from North America [P = 0.059; I2 = 88.7, Pheterogeneity = 0.003) . Two other studies [P = 0.391; I2 = 84.3, Pheterogeneity < 0.001). One study [P = 0.001)  and one case–control study [P = 0.927; I2 = 75.5, Pheterogeneity = 0.043) showed no association between prenatal mental disorder and childhood AD, whereas only one retrospective cohort study [P = 0.391; I2 = 84.3, Pheterogeneity < 0.001)  and two studies from North America [P = 0.187; I2 = 58.4, Pheterogeneity = 0.121) suggested that there was no correlation between childhood AD and prenatal mental disorder  mental illnesses on children’s physical health, revealing that prenatal mental disorder contributes to poor fetal growth and further suggesting the impact of maternal mental diseases during pregnancy on children . In the Nevertheless, this meta-analysis has limitations, and the results must be weighed against these limitations. All identified studies were observational and are therefore subject to confounding bias. Moreover, there were several retrospective studies. Factors such as selection bias, recall bias, and information bias were inevitably inherent in our analysis. Although we extracted the adjusted effect sizes for analysis, the covariates of each model were different. Some studies may be subject to over-adjustment, where analyses adjust for variables on the causal pathway between the exposure and the outcome. Although we actively tried to include unpublished research, all the identified studies were from the published literature. Therefore, it might well be that some positive findings are the result of publication bias. Furthermore, some caveats should be considered when interpreting the findings of subgroup analysis of childhood asthma since only Cookson et al.  reported2-adrenoreceptors [Some studies have reported that anxiety/stress during pregnancy can aggravate the activation of the hypothalamic–pituitary–adrenal (HPA) axis, leading to the release of cortisol, which the placenta cannot entirely metabolize, and may even promote the release of placental glucocorticoids and crosses to the fetus, in which they can influence the fetal brain development and may result in airway inflammation and hyperresponsiveness , 29. Mateceptors  expresseeceptors , 32. Theeceptors –35. Giveeceptors  or mighteceptors . These gThe present study is a systematic review and meta-analysis (which has not been previously prospectively registered) on prenatal anxiety or depression symptoms and childhood asthma or AD. In the nine studies’ final analysis, the relationship between prenatal mental disorder and childhood asthma was statistically significant compared with childhood AD. The present study results are consistent with the previous meta-analysis , furtherP = 0.001), the association was not statistically significant for the North American studies (P = 0.059) [The association between prenatal maternal depression and childhood asthma seems more significant but only included one study that met the criteria . In theo= 0.059) , 25. MorAlthough the results of this updated meta-analysis are consistent with the previous one , we limiIn conclusion, this meta-analysis supports that prenatal mental disorders increase childhood asthma risk, whereas no significant association was found for childhood AD.Additional file 1: Supplementary Figure 1. A). Sensitivity analysis of asthma. Sensitivity analysis suggested the results are robust. B). Sensitivity analysis of AD.Additional file 2: Supplementary Table 1a. NOS criteria for cohort study. Supplementary Table 1b. NOS criteria for quality of case-control study.Additional file 3: Supplementary Table 2. Search terms and strategy.


Plasmodium spp. and Ebolavirus (EBOV) interact is important for future outbreaks.Viral outbreaks present a particular challenge in countries in Africa where there is already a high incidence of other infectious diseases, including malaria which can alter immune responses to secondary infection. Ebola virus disease (EVD) is one such problem; understanding how Plasmodium spp. coinfection, 2) effect of EBOV/Plasmodium spp. coinfection on EVD pathology and the immune response, 3) impact of EBOV/Plasmodium spp. coinfection on the outcome of EVD-related mortality. Random effects meta-analyses were conducted with the R package meta to produce overall proportion and effect estimates as well as measure between-study heterogeneity.We conducted a systematic review in PubMed and Web of Science to find peer-reviewed papers with primary data literature to determine 1) prevalence of EBOV/Plasmodium yoeli infection was protective against morbidity and mortality via the IFN-γ signalling pathway.From 322 peer-reviewed papers, 17 were included in the qualitative review and nine were included in a meta-analysis. Prevalence of coinfection was between 19% and 72%. One study reported significantly lower coagulatory response biomarkers in coinfected cases but no difference in inflammatory markers. Case fatality rates were similar between EBOV(+)/Pl(+) and EBOV(+)/Pl(-) cases , and there was no significant difference in risk of mortality  although heterogeneity between studies was high. One in vivo mouse model laboratory study found no difference in mortality by infection status, but another found prior acute The literature was inconclusive; studies varied widely and there was little attempt to adjust for confounding variables. Laboratory studies may present the best option to answer how pathogens interact within the body but improvement in data collection and analysis and in diagnostic methods would aid patient studies in the future. Viral epidemics have been recognised as an increasing global public health threat. As has been observed during the COVID-19, SARS and MERS outbreaks, our increasingly connected world allows rapid international spread of viruses like never before . Spread lasmodium spp. co-infection to be high in these settings. Understanding how Plasmodium spp. (herein Plasmodium) infection may alter responses to viral infection, and vice versa, is thus important for their treatment and control. Insights into this may be inferred from Plasmodium’s interaction with other established viral infections. Outbreaks of Ebola virus disease (EVD) occur sporadically in countries in Africa where there is already a high burden of malaria. Historically, the majority of EVD outbreaks have been relatively small with case numbers typically less than 100 people ) AND . While this search strategy was very general, the number of returned articles was deemed feasible to screen without further narrowing of the search terms, thus ensuring all relevant papers could be identified. An initial screen of titles and abstracts excluded irrelevant papers based on being either: review papers, comments/editorials/correspondence, unrelated to EBOV or Plasmodium infection, research on vaccines or drug modes of action, not in the English language. Remaining papers were reviewed in their entirety and papers were included if they met the following criteria: 1) primary peer-reviewed research, 2) either i) epidemiological studies or genomic sequencing studies with explicit measurement of Plasmodium and EBOV co-infection prevalence and/or any measure of impact on EVD pathology/immune response/mortality, or ii) clinical case studies with disease pathology/immune response measures of co-infected patients, or iii) laboratory studies with ex vivo and/or in vivo models of EBOV and Plasmodium coinfection and a measure of effect on disease pathology and/or immune system modulation and/or mortality. Study of any Plasmodium or EBOV species and within any country and any date were included. In a subsequent meta-analysis, only epidemiological studies with prevalence of coinfection and CFR by malaria infection status and/or effect estimate data on the outcome of EVD-related mortality from countries in Africa were included. We did not include grey literature.The literature search was conducted with a final update on 15Plasmodium coinfection on EVD-related mortality; 10) other variables with a significant impact on mortality .All papers were included for qualitative review of methods and key findings. Observational cohort studies were also included for quantitative review in a meta-analysis. For the meta-analysis, data were extracted on the following variables: 1) study first author and publication details, 2) study design; 3) location and study period; 4) details of study population, including population size, mean age and sex breakdown; 5) source of data; 6) EVD-related data including method of diagnosis, EBOV species, number of EBOV positive (EBOV(+)) cases; 7) malaria-related data including method of diagnosis, Plasmodium species, number of sample that received a malaria diagnostic test, number of positive tests; 8) Mortality data including crude EVD case fatality rate (CFR), CFR of coinfected patients; 9) Effect estimates (e.g. risk ratios (RR), odds ratios (OR) and hazard ratios (HR)) for the effect of Extracted data were independently verified (i.e. double verification) by another member of the study team. Where necessary, study authors were contacted to verify study details. The authors conducted this meta-analysis in concordance with PRISMA standards of quality for reporting meta-analyses and the guidelines for Meta-Analyses and Systematic Reviews of Observational Studies , 23.Plasmodium coinfection among EVD cases (EBOV(+)/Pl.(+)), ii) crude CFR of EVD cases, iii) CFR of EBOV(+)/Pl.(+) cases and iv) CFR of EBOV(+)/Pl.(-) cases. This was conducted using the metaprop function from the meta package in R [We used a random-effects meta-analysis of proportions approach to quantify i) the prevalence of age in R , 25. Metage in R . MetaproPlasmodium infection on EVD mortality, where available, numbers of exposed (EBOV(+)/Pl.(+)) and unexposed (EBOV(+)/Pl.(-)) and with and without the outcome of death were used to calculate unadjusted RR and used in a random effects meta-analysis of RR using the metabin function within the meta package which allows meta-analysis of studies with comparison of two groups with binary outcomes [For effect estimates related to the impact of outcomes . Finallyoutcomes .2, Chi2 and Tau-squared (τ2) statistics. I2 is a measure of the percentage of variability in the effect sizes that is not caused by sampling error, where 25% is considered low heterogeneity, 50% moderate heterogeneity and 75% substantial heterogeneity [2 is not sensitive to the number of studies, it is sensitive to the precision of the included studies. Tau2 measures the between-study variance within a random effects model and is insensitive to the number and precision of included studies. The square-root of Tau2 is the estimated standard deviation of the underlying effects across all the studies [Heterogeneity between studies was quantified for each proportion and effect estimate measure using the Iogeneity , 29. Alt studies . In all  studies .Due to the small number of studies ultimately included in the effect size meta-analysis, publication bias via assessment of funnel plot asymmetry could not be assessed since the power to distinguish true asymmetry from chance is limited when the number of studies is <10 and is, therefore, not recommended . HoweverPlasmodium coinfection prevalence and/or impact on disease outcome according to our inclusion criteria , two laboratory studies and one clinical case report. A final set of nine cohort studies were included in the quantitative meta-analysis based on having a unique cohort of patients with similar patient characteristics. Studies were excluded if drawn from the same sampled cohort as another more up-to-date or larger study (n = 3), or if they sampled only children (n = 1).Nine retrospective cohort studies , 36–43 aSample size of the study cohorts varied from 52 to 2741 and EVD cases from 52 to 1512. Twelve of the studies included all age groups in their cohort, while one included only children aged <18 years. Percentage of males among EVD(+) cohorts was mostly between 44 and 52% (n = 5), although ranged from 13.5% to 63%.t) was analysed as a proxy for viral load. Cycle threshold is defined as the cycle number of the assay at which the fluorescence exceeds a certain threshold, with lower Ct values indicative of higher viral load and vice versa [Zaire ebolavirus ; only one investigated Bundibugyo ebolavirus (BDBV).EVD was diagnosed by real-time PCR (RT-PCR) in eleven cohort studies including seven studies , 46, 47 ce versa . The remPlasmodium infection considered to provide equivalent sensitivity to microscopy [Plasmodium to determine malaria infection prevalence.Malaria diagnosis was conducted by rapid diagnostic test (RDT) in most of these studies except two in which malaria diagnosis was made by qRT-PCR, with Ct ≤ 30 indicative of a positive croscopy , 38. ThePlasmodium falciparum (Pf) was specified as the causal agent of malaria in one cohort study [Pf although subsequent analyses included all species [Pf as the causal agent in their samples. The rest did not specify Plasmodium species in their analyses but all used RDTs that detect all four major Plasmodium species , Plasmodium malariae (Pm) and Plasmodium ovale (Po)), except one which used a HRP2 RDT detecting Pf only [rt study  and one  species . The mNG Pf only .Only one study  attempteOne cross-sectional national survey was identified in Gabon which covered a general rural population of 4,272 and measured past exposure to ZEBOV infection using seroprevalence of ZEBOV-specific IgG antibodies, and current Plasmodium spp. infection using in-field blood smear and Plasmodium mitochondrial DNA sequencing. DNA sequencing identified Pf, Pm and Po infections within the sample but main analyses included all-species Plasmodium but was also reported for Pf and Pm infections only.One clinical case report was identified describing the pathology of EVD and malaria coinfection during pregnancy. The clinical case report included one pregnant woman from Gulu, Uganda admitted with Sudan virus in 2000, and a second from Isiro, DRC, infected with BDBV in 2012. EVD was diagnosed using species-specific RT-PCR in each location as well as ELISA in Gulu. Histological methods were employed to analyse EVD and malaria pathology in placental and foetal tissues following delivery.Plasmodium infection on outcomes related to EVD. The model in one study was of CD1 mice infected via intraperitoneal inoculation with Plasmodium yoeli (Py) at a dose of 104 parasitized erythrocytes, followed by challenge with mouse-attenuated EBOV (MA-EBOV) at a 100 median lethal dose at different time points post Py infection. In each time-group, 6 mice were followed for survival to 28 days post infection (dpi), and four were euthanised on day 4-dpi to analyse blood and liver RNA concentrations for Py and MA-EBOV [Both laboratory studies used an in vivo murine model of coinfection to analyse the impact of prior  MA-EBOV .-I-), and IFN-γ receptor null mice (Ifngr-I-) inoculated intraperitoneally with a higher dose of 106 parasitized red blood cells of Py and challenged with MA-EBOV or recombinant vesicular stomatitis virus (rVSV)/EBOV glycoprotein (GP) at three different concentrations: 1-, 10- and 100-iu on the sixth day following Py infection. In each group, seven mice were followed for survival up to 18 days and three were euthanised on day 3 to determine viremia and viral load. Knock-out mice were used to study the signalling pathways implicated in initial lab findings. The study also analysed Ifnar-I- mice with P. chabaudi (Pcc) infection in the first round of experiments but found no difference in outcomes compared to Py so was discontinued. To test the durability of in vivo effects, parallel experiments challenged Py-infected mice with rVSV/EBOV GP at weeks 1, 3, 5, and 7 post-Py inoculation. In addition, an ex vivo model of infection was analysed using naïve human and mouse macrophages challenged with sera from parasitaemic rodents and from rhesus macaques infected with Plasmodium cynomolgi [The second laboratory study used wild-type, interferon (IFN-αβ) receptor knock-out mice  cohorts ranged from 18.9% to 72.2% for studies utilising malaria RDTs, and 15.4% and 19.4% for the two studies utilising qRT-PCR. In addition to these cohorts, RNA sequencing data from EBOV(+) cases in Guinea, found that 84% (156/186) contained reads mapping to Pf, higher than malaria prevalence found by RDT on the same sample of patients . However, read depth, a proxy for parasitaemia density, varied widely from 59 to 358820 FPKM (a measure for read depth) and the discrepancy between diagnostic methods reduced as number of reads mapping to Plasmodium increased. RNA sequencing in Boende, DRC, found 24.3% of EBOV(+) cases were coinfected with Pf. One study which focused only on children aged <18years found prevalence in this group to be 40%. Prevalence of Plasmodium infection was reported as higher in children aged and less common in EBOV(+) compared to EBOV(-) individuals [Thirteen cohort studies reported data on prevalence of coinfection. Prevalence of ividuals , 46.Plasmodium infection and ZEBOV-specific IgG antibodies, a significant overabundance than would be expected by chance .The cross-sectional survey found evidence of an epidemiological overlap of the two infections with 10.2% (n = 425) of adults in rural Guinea positive for both current Plasmodium coinfection among EVD patients varied from 18.9% to 44.4% between studies, with the overall meta-analysis estimate calculated at 21.7%, 95% CI 18.7–25.1%  were increased in abundance in EBOV(+)/Pf(-) cases, suggesting, vice versa, that Pf coinfection had an inhibitory effect on coagulation.In their metagenomic sequencing study, Li et al. found no significant differences in clinical characteristics  between EVD(+)/Pf(+) and EVD(+)/Pf(-) patients . DiffereAnimal models. One experimental lab study measured immune response biomarkers in infected mice and found that acute Plasmodium infection protected against a low but lethal dose (1-iu) of virus (both MA-EBOV and rVSV/EBOV) by eliciting the proinflammatory interferon gamma (IFN-γ) pathway, rendering cells resistant to EBOV infection [Plasmodium infection and/or a sustained level of IFN-γ confers protection against EBOV viral replication .nfection . MorbidiHuman subjects—CFR. Crude EVD-related mortality was reported in 12 cohort studies and ranged from 44%  to 72.8% . For BDBV infection, crude CFR was 53.8%  and in the study looking only at children aged <18 years crude CFR was 56.6% . CFR by Plasmodium infection status were reported in eleven cohorts and ranged from 42.2% to 85.7% for EBOV(+)/Pl(+) cases, and from 52.2% to 60.3% for EBOV(+)/Pl.(-) cases.2 at 68%, 95% CI 33–85%, Chi2 = 21931, p<0.01 and Tau2 = 0.02. The prediction interval was 48.7–66.0%.Eight of the cohort studies were included in a meta-analysis for CFR estimates . Overall2 = 75%, 95% CI 49–88%, Chi2 = 27.76, p<0.01, Tau2 = 0.2) but much lower for the CFR of singly-infected cases .CFRs by malaria infection status were estimated at 62.1%, 95% CI 50.1–72.8% for EBOV(+)/Pl.(+) cases and 56.7%, 95% CI 53.6–59.7% for EBOV(+)/Pl(-) cases . HeterogEach CFR was similar when looking only at ZEBOV species alone  and whenHuman subjects—effect estimates. Seven studies found no significant difference in CFR by Plasmodium infection status in unadjusted analyses [analyses , 45, 47.Plasmodium coinfection inhibited the apparent beneficial effect of ASAQ treatment; ASAQ treatment appeared to reduce mortality in EBOV(+)/Pl(-) cases compared to those treated with A-L whereas no beneficial effect was seen in EBOV(+)/Pl(+) cases.Two studies found no effect of coinfected in adjusted analyses. Hartley et al. found coinfection was associated with significantly higher mortality when adjusted only for age and sex , however, these individuals also had higher viral loads and once this was taken into account the detrimental effect was abrogated. Gignoux et al. found no effect after adjusting for multiple confounders including antimalarial prescription, age group, sex, Ct value at admission, days from symptom onset to admission, receipt of IV fluids, and number of inpatients at the Ebola treatment centre on day of admission . However, this study did find that Plasmodium coinfection on mortality with an elevated CFR (52% v 66%) and 28-day mortality . In a focused subgroup analysis, adjusted for age only, there was greater mortality among EBOV(+)/Pl(+) compared to EBOV(+)/Pl.(-) cases . Compared to EBOV(-)/Pl(-) patients, the hazard of dying was highest in EBOV(+)/Pl.(+) cases  followed by EBOV(+)/Pl.(-) cases . Kerber et al, meanwhile, found that Plasmodium coinfection only had an impact on mortality among 5–15-year-olds among whom it increased CFR by >20% and increased odds of death to 4.2 times greater than individuals of the same age group without Plasmodium co-infection. No other age groups appeared to be affected, suggesting an interaction between age and infection status.Two studies reported increased mortality in either the general study population  or in association with age  In the former, although no significant effect was found from a smaller study drawn from the same source population , with a larger sample Waxman et al., found a significant detrimental effect of Plasmodium infection was associated with an increased survival when adjusted for age, sex and EBOV viral load . However, the effect was more pronounced when stratified by plasmodium parasitaemia level, using Ct as a proxy. High Plasmodium burden was then associated with increased risk of survival to 1.4, 95% CI 1.2–1.7, p<0.0001) whereas low parasite burden infection did not have a significant effect  P = 0.007). These effect estimates did not include individuals aged <5 years due to low numbers of cases in that age group.In contrast, just one study found coinfected patients had significantly lower CFR than singly infected cases (p = 0.007) . PlasmodPlasmodium infection, studies also reported other significant variables affecting CFR as including age, viral load, aspects of clinical treatment  and certain clinical features (e.g. bleeding and other symptoms).In addition to 2 = 67%, 95% CI 26–85%, Chi2 = 18.09, p<0.01, Tau2 = 0.03) and a prediction interval of 0.68–1.74.For the meta-analysis, numbers of exposed/unexposed and with outcome data was extracted from seven cohort studies, all investigating ZEBOV . Individ2 = 24%, 95% CI 0–69%, Chi2 = 5.24, p = 0.26, Tau2 = 0.009) and slightly reduced prediction interval of 0.80–1.64 , these were excluded and the meta-analysis re-run only on the studies using RDT. This estimated a higher but still insignificant risk ratio of 1.15, 95% CI 0.98–1.35, with lower heterogeneity ) and an incomprehensibly wide prediction interval  MA_EBOV challenge but less so with moderate to high (10-iu and 100-iu) doses. This protective effect waned over time, with Py-infected mice protected from EBOV challenge three weeks after Py infection, but not by 5 weeks. This was IFN-γ dependent as discussed above.The eight studies included in the meta-analysis were analysed for quality using the Newcastle-Ottawa Scale . Four stPlasmodium coinfection on mortality from EVD which could have significant implications for future outbreaks of EVD and other viral outbreaks with similar pathology. The number of studies identified, particularly those for the meta-analysis, was limited. This could be because EVD outbreaks have historically been small and, indeed, the majority of studies stem from the 2014 West Africa EVD outbreak which had a huge affected population in comparison and a high level of support from national and international NGOs and research institutions [We have attempted to consolidate findings on the prevalence and effect of itutions , 52. EVDPlasmodium , and, aside from one, appeared relatively consistent across individual studies. Plasmodium spp. prevalence was lower in EVD confirmed cases compared to patients without EBOV infection, most likely because presenting symptoms were due to the viral infection and not malaria in the former group. Indeed, Hartley et al. found that malaria infection could be used as one variable (among others) to help distinguish EVD cases from other diagnoses [Overall, one-quarter of EVD cases were infected with iagnoses . DespitePlasmodium infection on mortality, while two found a significant detrimental effect, and one found a significant protective effect. Overall, the meta-analysis estimated that the CFR of coinfected patients was not significantly different from the CFR of EBOV(+)/Pl(-) patients, and a meta-analysis of effect sizes found no significant effect of coinfection on mortality . Although tests of heterogeneity have low statistical power with a small number of studies, use of the chi-square p-value and I2 confidence intervals can provide more confidence in these estimates and in this case suggest high heterogeneity between studies for both the overall effect estimate and the CFR of coinfected patients (EBOV(+)/Pl(+)) [From the cohort studies reviewed, the majority found no significant effect of )/Pl(+)) . ConversPlasmodium on EVD mortality. However, the difference in testing procedure doesn’t logically explain why Rosenke et al. would observe a protective effect from Plasmodium since RT-PCR is more sensitive than RDT, particularly in detecting low parasite density infection, and so could be expected to identify more malaria cases and would actually bias the effect estimate toward a detrimental effect  [In terms of study protocols, only two studies included in the meta-analysis used a malaria diagnostic that was more sensitive than RDT: qRT-PCR and a combination of RT-PCR and mNGS. One of these  (using Routcome) , 55. Conoutcome) , 57.Plasmodium infection compared to adults who gain some level of immunity to severe infection and are more likely to have a chronic, subpatent infection [Plasmodium infection.Additionally, the RT-PCR and mNGS tests could detect different stages of malaria infection to the RDTs, i.e. detecting sub-patent infection compared to more active/acute infection. These stages of malaria are associated with different immune responses which could affect EVD outcomes differently. Younger age groups are more at risk of acute nfection , 59. In nfection . This coPlasmodium infection is associated with activation of pro-inflammatory pathways and has been implicated in influencing response to other concurrent infectious agents such as respiratory viruses, enteric bacteria and HIV [Plasmodium infection was found to reduce viremia and associated pathologies of chikungunya virus, a more acute RNA virus, via proinflammatory responses through IFN-γ production [Plasmodium infection. Rosenke et al. looked at parasite burden (using Ct as a proxy) and found that higher parasite load (Ct ≤ 20), which would be expected from more acute infection, was associated with improved survival  compared to those with a lower parasite burden for which protection was not significant. A similar protective effect from acute infection was seen in the laboratory study by Rogers et al which found acute Plasmodium infection protected mice and human macrophages from EBOV challenge via a low but sustained IFN-γ response which protected from EBOV challenge up to three weeks post Plasmodium-infection but dwindled thereafter. However, in the only study to monitor similar human biomarkers, Carroll et al found that markers of the innate immune response to acute Plasmodium infection, including IFN- γ, were not different between Pf(-) and Pf(+) EVD cases whereas biomarkers associated with the coagulation pathway were reduced in patients Pf(+). This analysis thus suggests the inflammatory pathway found to be important in mice is perhaps not important in human cases, although, the analysis by Carroll et al was based on a very small sample size of individuals (10 and 13 per group).Acute  and HIV –20. HIV,oduction . DespitePlasmodium infection on mortality [The protective effect observed from the laboratory study by Rogers et al. was not observed in the second laboratory study identified, however, this second study used only a very high lethal dose of MA-EBOV (100-iu) . Use of ortality . The twoortality , 38. NotPlasmodium species and it could be expected that different species would be associated with a different proportion of chronic versus acute infections and differences in immune response. However, it is unlikely to explain differences in this context since the vast majority of malaria infection is caused by Pf in each of these countries [Due to the failure to adjust for important confounders, four of the eight studies included in the meta-analysis were deemed poor quality based on the Newcastle-Ottawa Scale analysis. As well as not adjusting for viral or parasite load, many of the studies failed to account for other potential confounders including age, sex, and time from symptom onset to admission. The majority of studies did not specify ountries . SimilarOutside of the cohort and laboratory studies, the case report of a pregnant woman in Uganda implicated other potential interactions between the two infectious agents in the placenta of pregnant women . It is uPlasmodium coinfection has an effect on EVD morbidity and mortality. Although pooled meta-analyses suggest no significant effect, there is a high amount of variability between study effect estimates that have not all had appropriate confounding variables considered, and/or had follow-up rates that may have biased results. With the advent of the new Ebola vaccine  which has shown high efficacy in trials, the clinical interaction of comorbidities with EBOV may have less significance in future EVD outbreaks [So, what does all this mean and what are the implications for future outbreaks of EVD and other viral diseases? From the literature as it stands, it remains unclear whether utbreaks . HoweverPlanning for research purposes is difficult in an outbreak setting where the outbreak is fast-moving and resources are limited but being better prepared with a planned set of guidance on what data should be collected prior to the next outbreak would enable faster implementation of data collection for subsequent research. Following analyses, all studies should be encouraged to publish all results related to these important factors, including raw numbers, unadjusted and adjusted estimates, to better enable meta-analytics.Even despite these improvements, due to the complex nature of the immune system, it may be that experimental lab methods will give the best insights. Findings by Rogers et al are interesting, but more comparison needs to be done to look into other disease models, as well as how well these animal models transfer to the human context. Mouse models of malaria and EVD do not mimic all facets of the diseases in humans, but findings from these models can be used to narrow down the field of investigation in the clinical setting—e.g. explicit measurement of immune system biomarkers such as IFN-γ, stratified by Plasmodium parasite load and viral load, should now be recommended in future clinical research.Remaining limitations on implementing better-planned research may be sample size restrictions if future outbreaks are not large enough, and diagnostic and clinical capacities to conduct the research. In this case, retrospective genomics analysis on stored blood samples may offer a useful tool since this is increasingly affordable and samples can be stored and analysed in retrospect or in partner institutions with greater research capacity. RNA/DNA read data can provide quantifiable information on prevalence of infection, viral and parasite loads, and biomarkers in one protocol, and thus perhaps be able to answer some of gaps in the data presented here.S1 Checklist(DOC)Click here for additional data file.S1 Fig(DOCX)Click here for additional data file.S2 Fig(DOCX)Click here for additional data file.


This work was aimed to synthetize the evidence available about the relationship between resting heart rate (RHR) and the risk of cancer mortality. A computerized search in the Medline, EMBASE, Web of Science, and Cochrane Library databases from their inception to 24 September 2020 was performed. We performed three meta-analyses: (1) cancer mortality comparing the “less than 60 bpm” and “more than 60 bpm” categories; (2) cancer mortality comparing “less than 60 bpm”, “60 to 80 bpm”, and “more than 80 bpm” categories; and (3) analysis for 10–12 and 20 bpm increase in RHR and risk of cancer mortality. Twenty-two studies were included in the qualitative review, and twelve of them met the inclusion criteria for the meta-analysis. Our results showed a positive association between RHR and the risk of cancer mortality. This association was shown in a meta-analysis comparing studies reporting mean RHR values below and above 60 bpm, when comparing three RHR categories using less than 60 bpm as the reference category and, finally, in dose response analyses estimating the effect of an increase of 10–12 bpm in RHR, both in men and in women. In conclusion, a low RHR is a potential marker of low risk of cancer mortality. Resting heart rate (RHR) is a fundamental clinical marker and an indicator of health or disease; in fact, high RHR is usually related to disease, and a low RHR is associated with better health . AssessiThe etiology of cancer involves, in addition to genetic factors, some environmental/lifestyle risk factors, such as physical activity, that are associated with the incidence of this disease ,3. AmongCardiorespiratory fitness is a direct measure of aerobic functional capacity ,7, whichSince cardiorespiratory fitness is a solid predictor of all-cause morbidity and mortality in several diseases, including cancer, just as physical activity is ,11,12, aThis systematic review and meta-analysis was registered through the International Prospective Register of Systematic Reviews-PROSPERO (CRD42018095756). This meta-analysis was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)  and MetaStudies were identified in the following databases from their inception to 24 September 2020: MEDLINE (via PubMed), Web of Science, EMBASE, and Cochrane Library. The search strategy included (“heart rate” OR “pulse” OR “resting heart rate” OR “beats”) AND  AND (“risk” OR “incide*” OR “cohort” OR “follow-up study” OR “prospective”). The literature search was complemented by scanning the reference list of published full-text articles and systematic reviews for relevant studies.The systematic literature search was independently conducted by two reviewers (D.P.P.-C. and I.C.-R.), and disagreements were resolved by consensus; if necessary, a third researcher (V.M.-V.) was asked to evaluate the study in question. Reviewers were not blinded to authors, journals or institutions. The articles included were follow-up studies that analyzed the site-specific risk of cancer and/or cancer mortality associated with the RHR. The criteria for the exclusion of studies were as follows: (i) studies not written in English, French, Portuguese, or Spanish; (ii) studies not reporting the incidence of cancer or cancer mortality; (iii) studies not reporting the RHR; (iv) non-follow-up studies or studies that did not report empirical data ; (v) studies including patients with stablished cancer diagnosis at the beginning of the study; and (vi) duplicate reports of the same study. For the meta-analysis, when some studies had published multiple reports, we used the study that provided more detailed data and had the largest sample size.Data extraction was performed independently by two authors (D.P.P.-C. and I.C.-R.) using a standardized data collection form. The following data were collected from each selected study: (i) name of the first author and year of publication; (ii) country; (iii) study name; (iv) period of data collection; (v) characteristics of the population: sample size, age mean, sex, race, and comorbidities; (vi) data concerning heart rate  and cancer ; and (vii) main study exposures and outcomes. When some information was lacking, we emailed the corresponding author requesting the data.We used the validated Newcastle-Ottawa scale for cohort studies to assess the quality of the included studies . This scDue to the cut-offs used for RHR categories and the effect size measures in the studies included, we performed the following three strategies for dose-response analyses: (1) analysis of cancer mortality comparing the “less than 60 bpm” and “more than 60 bpm” categories; (2) analysis of cancer mortality comparing the “less than 60 bpm”, “60 to 80 bpm”, and “more than 80 bpm” categories; and (3) cancer mortality risk analysis for each 10–12 and 20 bpm increase in the RHR. The analysis strategy was established following these considerations:When the studies provided odds ratios (ORs), these were converted to relative risks (RRs) to be combined in the meta-analysis . For theWhen studies presented several statistical risk-adjustment models, we considered the one including the largest number of additional covariates.To calculate the mortality pooled risk estimates by RHR categories (“less than 60 bpm” and “more than 60 bpm”), we only considered studies providing the risk of cancer mortality compared to the same reference level of RHR. Nevertheless, to calculate the pooled estimate by three categories of bpm , we included studies that, while not reporting risk measures for exactly the same categories, did report risk estimate measures for RHR in the ranges that we have established for those three categories. When the studies provided the data as an increment of RHR , we calculated two pooled HR subgroups: one for studies that reported an increase of 10–12 bpm and another for studies that reported an increase of 20 bpm, both in overall and by sex.The DerSimonian and Laird random effects method was used to compute pooled estimates of HRs or RRs and their respective 95% confidence intervals [95% confidence interval (CI)] for cancer mortality associated with RHR levels. The heterogeneity of results across studies was evaluated using the I2 statistic and was categorized as might not contain heterogeneity (0–40%), may represent moderate heterogeneity (30–60%), may represent substantial heterogeneity (50–90%), and may represent considerable heterogeneity (75–100%) . In addiSensitivity analyses  were conducted to assess the robustness of the summary estimates. The results of the sensitivity analyses were considered meaningful when the resulting estimates were modified beyond the CIs of the original summary estimate.Finally, publication bias was evaluated through visual inspection of funnel plots and by using the method proposed by Egger . StatistThe procedures used to measure the RHR were very varied: in four studies, RHR was measured manually ,21,28,37All studies included in the meta-analysis received equal or more than six points based on the Newcastle-Ottawa scale, which indicates that the studies included were of high quality .Among the 22 studies included in the systematic review, three studies reported all cancer incidences ,33,35. IUnfortunately, a meta-analysis of data regarding cancer incidence was not possible because the studies reported these results using different reference categories of RHR levels.-Cancer mortality comparing the “less than 60 bpm” and “more than 60 bpm” categoriesData about cancer mortality were analyzed using three different strategies: (i) we performed a meta-analysis including studies that reported cancer mortality by categories of mean RHR (≤60 bpm versus > 60 bpm); (ii) a second meta-analysis compared the risk of cancer mortality using three RHR categories (<60 bpm (reference level), 60–80 bpm, and >80 bpm); (iii) finally, an analysis was conducted assessing the effect of 10–12 and 20 bpm increase on cancer mortality risk.p < 0.001) (p = 0.093). The pooled RR estimate was not significantly modified in magnitude or direction when individual study data were removed from the analysis one at a time . Seven prospective studies were included in this meta-analysis ,34,36,38< 0.001) . Evidencp = 0.000) and 1.18  for men and women, respectively. The heterogeneity was not substantially modified when the gender subgroup analyses were performed.A subgroup by gender was performed, even though only three studies included women in their sample. Aimed to explore the high heterogeneity several subgroups analysis by type of measurement tool and type of cancer were attempted, but there were not enough studies in each group to perform them.-Analysis for 10–12 and 20 bpm increase and cancer mortalityAdditionally, p = 0.121) and for 20 bpm increase was 1.10 . Subgroup analysis by sex showed pooled HRs for an increase of 10–12 bpm of 1.14  for men and 1.09  for women; and for an increase of 20 bpm of 1.19  for men and 0.97  for women (p = 0.094). The pooled HR estimate was not significantly modified in magnitude or direction when individual study data were removed from the analysis one at a time .Six prospective studies reported data about cancer mortality by increments of RHR in bpm ,28,32,39or women . There wOur analyses show a positive association between RHR and the risk of cancer mortality, suggesting that a RHR less than 60 bpm seems to be a protective factor against the risk of cancer mortality. Similar result was found when comparing three RHR categories using less than 60 bpm as the reference category and, finally, in analysis estimating the effect of an increase of 10–12 bpm in the RHR on cancer mortality. Nevertheless, in these two last analyses, some inconsistencies can be observed, because while In a previous meta-analysis aimed at assessing the relationship between RHR, the risk of cardiovascular disease and cancer mortality provided similar estimates of increase in the risk of cancer mortality to our study , but it The mechanisms underlying the relationship between heart rate and cancer are complex and not entirely understood. It has been suggested that an elevated RHR indicates increased sympathetic activation and, consequently, an autonomic imbalance that has been associated with elevated risk not only of cardiovascular events but also of cancer and all-cause mortality . FurtherIn recent decades, there has been growing evidence showing a positive association between RHR and all-cause mortality ,46. HoweBecause genetic determinants of RHR could be involved in the origin of cancer  and becaOur study shows that a RHR lower than 60 bpm seems to be a protective factor against the risk of cancer mortality, nevertheless this analysis shows a high heterogeneity, which could be caused by the variability among studies in the strength of the association rather than the disparity in the effect´s direction. There exists the possibility that some part of heterogeneity may be due to clinical differences such as, age, duration of follow-up, type of cancer, or other confounders. When the subgroup analysis by gender was performed, a slight reduction in heterogeneity was shown , neverthAnother important recognized confounder is the cardiorespiratory fitness level. A previous meta-analysis concluded that moderate and high levels of cardiorespiratory fitness reduce the risk of lung, colorectal, and all cancer sites . Lower ROur findings suggest that a high RHR is a risk biomarker not only for cardiovascular disease and all-cause mortality ,52,54 buThis meta-analysis has several limitations that should be highlighted. First, the studies used different RHR levels as reference values for their estimates (HR or RR), which limited the number of studies eligible for inclusion in the meta-analysis. Second, cancer risk is related to several lifestyle habits, such as smoking, physical activity, and a healthy diet ; thus, aIn conclusion, our findings suggest that the RHR is associated with cancer mortality and could be related to the incidence of some types of cancer. Likewise, this study suggests the potential use of the RHR as a prognostic factor for cancer in clinical settings. Future studies are needed to verify the association of the RHR with cancer incidence and to determine feasible and efficient strategies to modify the RHR to improve cancer progression and overall survival.The wide use of exercise trackers and personal heart rate monitors makes research in the field of heart rate important not only for practitioners but also for individuals. Because the clinical accuracy of cut-offs for use in clinical practice has not been fully assessed, an RHR < 80 bpm could be used as a positive prognostic indicator in cancer patients.


IL6 gene  have been shown to be independently associated with coronary artery disease (CAD) by several investigators. Despite more than 12 published meta-analyses on this subject, association of -174 G/C with CAD, especially amongst distinct ancestral population groups remain unclear. We, therefore, conducted a systematic review and an updated meta-analysis to comprehensively ascertain the association of IL6 -174 G/C with CAD and circulating IL-6 levels.Circulating IL-6 levels and at least one polymorphic form of Relevant case–control/cohort studies investigating association of -174 G/C with CAD and circulating IL-6 levels were identified following a comprehensive online search. Association status for CAD was determined for the pooled sample, as well as separately for major ancestral subgroups. Association status for circulating IL-6 levels was assessed for the pooled sample, as well as separately for CAD cases and CAD free controls. Study-level odds ratios (OR) and 95% confidence intervals (CI) were pooled using random/fixed-effects model.p = 0.002) as well as allelic genetic model comparisons . This effect was largely driven by Asian and Asian Indian ancestral subgroups, which also showed significant association with CAD in both genetic model comparisons . Other ancestral subgroups failed to show any meaningful association.Quantitative synthesis for the CAD endpoint was performed using 55 separate qualifying studies with a collective sample size of 51,213 . Pooled association of -174 G/C with CAD was found to be statistically significant through dominant  as well as in the CAD free control subgroup , though not in the CAD case subgroup .Circulating IL-6 levels were found to be significantly higher amongst the ‘C’ allele carriers in the pooled sample (Standard mean difference, SMD 0.11, 95% CI 0.01–0.22 pg/ml, IL6 -174 G/C polymorphism and CAD, which seems to be mainly driven by Asian and Asian Indian ancestral subgroups. Upregulation of plasma IL-6 levels in the ‘C’ allele carriers seems to be at least partly responsible for this observed association. This warrants further investigations with large, structured case–control studies especially amongst Asian and Asian Indian ancestral groups.The present systematic review and meta-analysis demonstrate an overall association between The online version contains supplementary material available at 10.1007/s00011-021-01505-7. IL6 gene (located at chromosome 7p21–14) which is known to have several polymorphic variants . . On the other hand, Mixed ancestry subgroup [nst = 1, OR range 0.42–0.55, Z value range = 2.71–3.50, p value range = 0.007–0.0005). Other ancestral subgroups such as European ancestry [p value range = 0.11–0.47).  (Supplementary Table 2).Similarly, summary effect measures for all ancestral subgroups, respectively, were also obtained using appropriate effects for analysis. Results obtained for Asian ancestry –59, 72 asubgroup  showed aancestry –48, 69, ancestry –53 and Aancestry  did not nst = 9; 3418 subjects) [nst = 6; 3389 subjects) [Z value = 2.14, p = 0.03). While CAD case subgroup did not yield significant association (p = 0.12), IL-6 levels were found to be significantly higher amongst the ‘C’ allele carriers in the CAD free control subgroup  as shown in Fig. p value range = 0.663–0.918)  , 66, 74 ubjects) , 66. ‘C’p values for each qualifying group/subgroup constructed for -174 G/C for CAD endpoint are displayed in Fig. p values seem to reach statistical significance for most of the ancestral groups and subgroups which could have been a direct result of inherent heterogeneity. This indicates that the use of ancestral stratification was also not sufficient to tone down the possible existence of bias. On the other hand, we found no evidence of publication bias in subgroups constructed for circulating IL-6 endpoint.Each group or subgroup with ≥ 3 included studies was assessed for existing publication bias using Begg’s funnel plot test  and EggeSensitivity analysis was performed in each study group/subgroup with ≥ 5 included studies. Studies were excluded one after another in these groups/subgroups and the analysis was repeated after each omission. We observed no instance of significant alteration from the original results, i.e. from lack of association to significant association or the other way around for both endpoints, which is an indicator of the robustness of the meta-analysis in question (Data not shown).IL6 -174 G/C polymorphism with CAD as well as circulating IL-6 levels. The main findings were: (i) pooled results indicated a significant association of -174 G/C polymorphism with CAD; however, the effect was driven by studies with participants belonging to Asian and Asian Indian ancestries; (ii) other major ancestries, including European and Middle Eastern displayed no evidence of such association; (iii) ‘C allele’ carriers, at least amongst CAD free controls seem to have significantly higher levels of circulating IL-6, which in part explains the association of this SNP with CAD.We present the most comprehensive and structured meta-analysis on the association between p ≤ 0.0005, for both genetic models), in contrast to a milder level of associations (p = 0.01 in both models) reported by Hou et al. [Results obtained in our meta-analysis for the CAD endpoint are much more robust than the recent one on this subject , which iu et al.  Second, u et al. , who cluIL6 gene at positions 597, 572, 373 along with 174 bp, have been known to influence IL6 transcription through complex interactions determined by the haplotype [IL6 gene; are, therefore, associated with higher plasma concentrations of circulating IL-6, thus making them more susceptible to the development of atherosclerotic disease. We tested this hypothesis and found that while possibly the influence of concomitant medications [p = 0.12), our CAD free control subgroup showed a clear association of ‘C’ allele carriers with elevated circulating IL-6 levels (p = 0.009).At least 4 promoter polymorphisms of the ications , preventIL6 mRNA expression is 10–40 fold higher in atherosclerotic as compared to healthy arteries [IL6 gene SNPs on the regulation of plasma IL-6 levels have also been investigated before [IL6 polymorphic sites  have complex interactions between each of their transcriptional machineries [IL6 promoter haplotypes have been reported to be better predictors of transcription levels of IL6 gene [This difference has also been observed locally at the transcriptional level where arteries . IL-6 noarteries . It has arteries . The effp values were seen for both genetic model comparisons in most of the analyzed groups/subgroups.Meta-analyses on genetic association studies tend to have significant limitations. First, for some ancestral subgroups—only a few published reports with moderate sample sizes were available; their meta-analysis results should thus be interpreted with caution. More studies from these ancestral groups are warranted to establish these derived associations. Second, the fact that meta-analyses of association studies cannot inspect interference of linkage disequilibrium, it constitutes as a major limitation. Third, the presence of selection bias in individual included studies and the presence of publication bias in a meta-analysis of non-randomized, genetic association studies easily qualify to be the most important limitation. Several statistical tools are available to test publication bias, although none are perfect, are easily influenced by heterogeneity, and in our case two of them were used which gave inconsistent results. This fact illustrates that the role of existing publication bias cannot be completely ruled out. We cannot be sure whether to trust our funnel plots where most of the studies were contained within the inverted cone, signaling a lack of publication bias or the results of the Egger’s test where significant IL6-174 G/C variant with CAD was observed in the pooled results of our present meta-analysis, largely driven by studies belonging to Asian and Asian Indian ancestral subgroups. Upregulation of plasma IL-6 levels in the ‘C’ allele carriers seem to be at least partly responsible for this seen association. Further investigations are warranted with large structured case–control studies especially amongst populations belonging to Asian and Asian Indian ancestry.Significant association of IL6 -174 G/C polymorphism with CAD employing a dominant genetic model (CC+GC vs. GG). Effect sizes for “Pooled” as well as for European and Asian Indian ancestral subgroups displaying a high level of heterogeneity were estimated using random effects for analysis. Effect sizes for Middle Eastern, Asian, African and Mixed ancestral subgroups were estimated using fixed effects. (PPTX 127 KB)Supplementary Figure 1. Forest plot depicting associations of IL6 -174 G/C polymorphism with CAD employing an allelic genetic model (Allele C vs. Allele G). Effect sizes for “Pooled” as well as for European and Asian Indian ancestral subgroups displaying high level heterogeneity were estimated using random effects for analysis. Effect sizes for Middle Eastern, Asian, African and Mixed ancestral subgroups were estimated using fixed effects. (PPTX 127 KB)Supplementary Figure 2. Forest plot depicting associations of IL6 -174 G/C polymorphism separately amongst CAD cases and CAD free controls. Standard mean difference for “Pooled” as well as CAD case subgroup were estimated using random effects owing to high levels of inherent heterogeneity. Standard mean difference for CAD free control subgroup which displayed low levels of inherent heterogeneity were estimated using fixed effects. (PPTX 65 KB)Supplementary Figure 3. Forest plots depicting differences in circulating IL-6 levels amongst ‘C’ allele carriers and GG homozygotes. Comparison of IL-6 levels in CC+GC vs. GG genotypes of Supplementary Table 1 (DOCX 15 KB)Supplementary Table 2 (DOCX 15 KB)Below is the link to the electronic supplementary material.


Objectives: The aim of the present meta-analysis was to synthesize results from the association between problem gambling (PG) and dimensions of the five factor model of personality and to identify potential moderators  of these associations in meta-regressions.Methods: Searches were conducted in six databases; Medline, Web of Science, PsychInfo, Google Scholar, OpenGrey, and Cochrane Library . Included studies: (1) reported a relationship between PG and at least one of the personality traits in the five-factor model, (2) contained information of zero-order correlations or sufficient data for such calculations, and (3) were original articles published in any European language. Case-studies, qualitative studies, and reviews were excluded. All articles were independently screened by two authors. Final agreement was reached through discussion or by consulting a third author. Risk of bias of the included studies was assessed by the Newcastle-Ottawa Scale. Data were synthesized using a random effects model.Results: In total 28 studies, comprising 20,587 participants, were included. The correlations between PG and the traits were as follows: Neuroticism: 0.273 , conscientiousness −0.296 , agreeableness −0.163 , openness −0.219 , and extroversion −0.083 . For all meta-analyses the between study heterogeneity was significant. Presence of gambling diagnosis was the only moderator that significantly explained between-study variance showing a more negative correlation to extroversion when participants had a gambling diagnosis compared to when this was not the case.Discussion: The results indicated some publication bias. Correcting for this by a trim-and-fill procedure showed however that the findings were consistent. Clinicians and researchers should be aware of the associations between personality traits and PG. Previous studies have for example showed neuroticism to be related to treatment relapse, low scores on conscientiousness to predict treatment drop-out and agreeableness to reduce risk of treatment drop-out.Systematic Review Registration: PROSPERO (CRD42021237225). A summary of the characteristics of each study, including country, publication, sample sizes of PG, and control group, instrument used for assessment of personality and gambling problems, number of personality dimensions measured, and the measure of effect size, is provided in SD = 1.69). The agreement between raters were 78.6% for “selection,” 100.0% for “comparability,” and 96.4% for “outcome,” respectively.The Newcastle-Ottawa Score results for each study are shown in CI = 0.182, 0.358). Cochran Q was significant . The I2 was 95.78% indicating a high heterogeneity. The funnel plot .The results of the meta-analysis on the personality trait neuroticism are presented in nel plot  suggesteCI = −0.400, −0.185). Cochran Q was significant , suggesting significant heterogeneity across studies. The I2 was 96.670%, indicating a high heterogeneity. The funnel plot .The results of the meta-analysis on the personality trait conscientiousness are shown in nel plot  suggesteCI = −0.223, −0.101). Cochrans' Q was significant , suggesting heterogeneity. The I2 was 86.229%, indicating high heterogeneity. The funnel plot .The result of the meta-analysis on the personality trait agreeableness are presented in nel plot  suggesteCI = −0.308, −0.127). Cochran Q was significant , suggesting significant heterogeneity. The I2 statistic was 88.790%, indicating a high heterogeneity. The funnel plot .The results of the meta-analysis on the personality trait openness are presented in nel plot  suggesteCI = −0.120, −0.046). Cochran Q was significant , suggesting heterogeneity. The I2 was 55.373%, indicating a moderate heterogeneity. The funnel plot , conscientiousness , agreeableness , and openness  the regression model was not significant. The regression model was however significant for extroversion . Only the predictor, diagnosis, was significant , suggesting more negative effect sizes for samples with participants with a gambling diagnosis than for samples without a gambling diagnosis. There was still significant unexplained between-study variance for extroversion .Because of the significant heterogeneity in all meta-analyses, a meta-regression analysis based on a random-effect model was conducted for each trait. The results are presented in |r| > 0.25) correlations were found for conscientiousness (r = − 0.296) and neuroticism (r = 0.273) whereas the smallest correlation (|r| < 0.10) was found for extroversion (r = 0.083). The results for each dimension are further discussed in detail below.This quantitative review examined the correlation between PG and the dimensions of the five-factor model of personality. A total of 28 studies fulfilled the inclusion criteria. Four of the five postulated hypotheses were supported. All five meta-analyses turned out significant. The two strongest  was supported with an overall y nature . Gambliny nature , 21. They nature  and Specy nature . In termH2 (expecting an inverse association between PG and conscientiousness) was supported with an overall correlation of −0.296. Müller et al.  indicateThe results further supported H3 (expecting an inverse association between PG and agreeableness), with an overall correlation of −0.163. Individuals low on agreeableness are often characterized by being competitive, challenging, and less cooperative with others . GamblinH4 (expecting an inverse association between GP and openness) was also supported with an overall correlation of −0.219. In general, individuals with a high score on openness are more open-minded to new people and new experiences, in addition to being imaginative, intellectual, and creative . Accordir = −0.083). An a priori assumption was that a positive correlation between extroversion and GP would be in agreement with the notion of extroverts as individuals searching for social, exciting settings, which conceivably could lead to high gambling involvement. Also, extroversion is generally found to be associated with some addictions (H5 (expecting a positive association between GP and extroversion) was not supported by the findings as the overall correlation was negative , in order to be able to explain larger proportions of the between-study variances.The studies included in the present meta-analysis originated from a variety of countries. Still, few studies were conducted in non-Western and developing countries. Furthermore, the studies showed a broad variation in terms of study quality, as shown by the Newcastle-Ottawa assessment in The present meta-analysis has several strengths. It was conducted in line with the PRISMA guidelines . SearcheThe main limitation of the present meta-analysis is that definitions of PG were not the same across studies. It cannot be ruled out that the associations between PG and personality may vary as a function of the various operationalizations of both PG and personality. The large number of operationalizations did, however, preclude meaningful subgroup analysis of results from specific operationalizations. In addition, there were few studies comprising randomized samples. In addition, the target population (problems gamblers), consisted of various types of gamblers, reflecting large heterogeneity in terms of types/groups of gamblers. This implies restrictions in terms of external validity. Also, limited generalizability relates to the broad usage of personality measures and the large range of gamblers included . Another limitation pertains to the screening process of relevant studies, which initially was based on title and abstract. Hence, it cannot be ruled out that a few relevant studies may have been excluded, although relevant information usually is presented in the title or abstract. A final limitation is that the funnel plots showed asymmetry in four out of five meta-analyses, suggesting publication bias. The trim and fill procedure did however aim to correct for this. The discrepancies between the original and adjusted effect sizes were small to moderate, suggesting that the data and conclusions were not influenced by publication bias.The positive association between PG and neuroticism should alert clinicians to the vulnerability of those suffering from PG regarding experiencing dysphoric states. Therapists should therefore consider to address this vulnerability specifically. In this context clinicians should also be aware that many gamblers gamble in order to escape dysphoric emotional states . NeurotiThe present meta-analysis integrated and synthesized previously findings on the association between PG and the personality traits of the five-factor model, showing significant correlations between all the five personality traits and PG. The postulated hypotheses were supported for four of the traits, albeit not for extroversion. Only one of the moderators (diagnosis) turned out significant for one personality dimension (extroversion), suggesting the need to identify relevant moderators in future research. The results have implications for understanding of vulnerabilities related to development of gambling problems and shed important light on issues related to prevention and treatment .The meta-analysis datasets for this review study can be provided by contacting the corresponding author.SP assisted by RS, KB, AR: conceptualization. RS, KB, and AR: literature search and study coding. RS, KB, and AR assisted by SP: data analysis. All authors drafting and critically revising the manuscript, finalizing the paper and approval of submitted version.This study was funded by the Norwegian Competence Center for Gambling and Gaming Research, University of Bergen, Norway.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.