Experiencing maltreatment during childhood exerts substantial stress on the child and increases the risk for overweight and obesity later in life. The current study tests whether hair cortisol—a measure of chronic stress—and its metabolite cortisone mediate the relation between abuse and neglect on the one hand, and body mass index (BMI) on the other.The sample consisted of 249 participants aged 8 to 87 years . We collected data on child abuse and neglect using questionnaires, measured cortisol and cortisone concentrations in hair, and BMI. In a structural model, the effects of abuse and neglect on hair cortisol, hair cortisone, and BMI were tested, as well as the covariance between hair cortisol and BMI, and hair cortisone and BMI.p < .001) and higher BMI . Neglect was not related to hair cortisol, hair cortisone, or BMI. Hair cortisol and cortisone did not mediate the association between maltreatment, and BMI. Sensitivity analyses demonstrate the same pattern of results in a subsample of adult participants currently not living with their parents. However, in younger participants who were still living with their parents, the associations between abuse and cortisone  and abuse and BMI  were no longer significant.Within the sample, 23% were overweight but not obese and 14% were obese. Higher levels of experienced abuse were related to higher cortisone concentrations in hair (β = 0.24, These findings confirm that experiencing abuse is related to higher BMI but suggest that hair cortisol and cortisone are not the mechanism underlying the association between child maltreatment and BMI. This is the first study to show abuse may be associated to elevated concentrations of hair cortisone—evidence of long-term alterations in chronic stress levels. Future research may benefit from exploring the effects of maltreatment on weight gain in longitudinal designs, including measures of other potential mediators such as eating as a coping mechanism, and more direct indicators of metabolic health. Abuse and neglect are adverse childhood experiences that exert substantial stress on the child, and violate expectations of a safe and stable environment , 2. ExpeOverweight and obesity present a global health challenge with rising prevalence  and withIf abuse and neglect are encountered during developmentally sensitive periods, they have the potential to not only elicit an acute stress response but also to reprogram one of the central human stress response systems: the hypothalamic–pituitary–adrenal axis . When cThe majority of the above described research has investigated HPA-axis functioning by measuring circulating cortisol in saliva, which offers insight into acute cortisol levels across the day and in response to specific stressors. In recent years, measures have been complemented by assessing cortisol concentrations in hair samples, which represent a more chronic measure of cortisol , 35. CorSeveral studies have found associations between experienced maltreatment and hair cortisol levels later in life e.g., , 37. A mIn addition to cortisol levels, cortisone levels may be relevant in the context of maltreatment and BMI. Cortisol can be metabolized into the inactive cortisone by 11β-hydroxysteroid dehydrogenase (11B-HSD) type 2 . EssentiStress and cortisol also play a central role in obesity. Early evidence of the causal role cortisol plays in obesity comes from studies observing weight gain in patients who are administered glucocorticoids –42. AddiThe current study adds to the existing research by testing the mediating role of hair cortisol—as an objective measure of chronic stress and HPA-axis functioning—in the relation between retrospectively measured maltreatment and the BMI of children and adults. To our knowledge, only one study has investigated cortisol dysregulation as a mediator between maltreatment and BMI . This stWe expected that abuse and neglect experienced in childhood would be associated with higher BMI at the time of the study. Further, we expected that abuse and neglect would be related to hair cortisol and cortisone concentrations and that these would in turn be related to BMI. We hypothesize that the effect of maltreatment on BMI would be mediated by elevated hair cortisol and cortisone concentrations. Given mixed results in previous research, we explored whether abuse and neglect had differential effects.It has been argued that the initial response to experiencing maltreatment is an increased stress reaction, but that over time chronic stress results in down-regulation , 32, 58.The sample of the current study was drawn from the Dutch 3G Parenting Study that investigates intergenerational transmission of parenting styles, stress and emotion regulation using a multi-generational design , aged 8 to 87 years .Participants attended one or two 7-hour lab visits at the Leiden University Medical Center with their nuclear families. During these lab visits, participants completed questionnaires, computer tasks, interviews, and family interaction tasks. In addition, samples of hair, saliva, and buccal cells were collected. All participants signed informed consent. Parents cosigned informed consent if the participant was under the age of 18 years. Also, maltreatment questionnaires of underage participants were inspected after each lab visit. Ethical approval was obtained from the Ethics Committee of the Leiden University Medical Centre (reference number: P11.134).We measured child maltreatment experiences with a combination of two self-report questionnaires: the Parent-Child Conflict Tactics Scales CTSPC,  and the r(247) =.64, p < .001) and the average for physical and the average for emotional neglect (r(247) =.38, p < .001), respectively. Cronbach's αs show acceptable internal consistency for child-report  and parent-report .To measure maltreatment, we used a multi-informant approach in which we combined child- and parent-reports. All participants reported on whether they had experienced maltreatment . For the child-report score, participants reported on maternal and paternal behavior separately. Per subtype, we first calculated averages for maltreatment perpetrated by mother and maltreatment perpetrated by father. Then, per subtype, the higher score of mother or father was included in the child-report score. In addition, if a participant participated with a parent, that parent also reported on whether they had perpetrated maltreatment towards that particular participant . The same approach was used to calculate the parent-report score. At least one parent score was available for 61% of the participants. Child-report and parent-report were averaged. Lastly, abuse and neglect scores were calculated by averaging the average for physical and the average for emotional abuse  for 18 h at 25°C while gently shaking to extract cortisol and cortisone. In line with previous research e.g., , 57, we At a growth-rate of approximately one centimeter per month, one centimeter of hair represents the cumulative cortisol secretion of the past month . It is p2). BMI and age were correlated . When assessing BMI in children and adolescents, it has been recommended to use age and gender specific scores based on external reference values , RMSEA = 0.90, and CFI = 0.78). Of all the confounding variables, only season (summer vs. other season) was significantly related to cortisol  and medication use was related to cortisone . This is in line with the preliminary analyses . To assess SES we asked participant of 18 years and older about their household income and highest completed education. Yearly household income was measured on a 7-point scale ranging from (z > ± 3.29) were winsorized  indicating that data was MCAR. Therefore, we imputed missing values using full information maximum likelihood (FIML).The missing information were as follows: 2.4% hair cortisol, 1.2% hair cortisone, 5.6% BMI, 1.2% hair dyed, 1.2% hair bleached, 0.8% hair permed, 0.4% hair washing frequency, 0.4% on last hair wash, and 0.8% on hair product use. Little's missing completely at random (MCAR) test was not significant  because some of the variables had a non-normal distribution. To assess fit, we inspected comparative fit index (CFI) and the root mean square error of approximation (RMSEA). A CFI above .90 and an RMSEA below .06 was considered to describe a good fit between the model and the observed data .ps < .01). SES was negatively related to neglect and BMI-z (ps < .05). Abuse and neglect were correlated (p < .01) as were cortisol and cortisone (p < .01). Lastly, abuse was correlated to cortisol, cortisone, and BMI-z (p < .05) whereas neglect was only related to cortisone (p < .05). For participants who were younger than 21 years, a BMI SDS of 1 or higher was considered overweight and of 2 or higher was considered obese (z) in the analyses for optimal power , RMSEA = 0.00, and CFI = 1.00. The complete model with standardized path coefficients is presented in The hypothesized model fit the observed data well with z scores . Age and sex were not included as covariates as BMI-z was already corrected for age and sex. There was a significant positive association between abuse and BMI-z  with higher levels of experienced abuse predicting higher BMI-z. The effect of experienced neglect on BMI-z was not significant . Hair cortisol and hair cortisone were not associated with BMI-z .Lower SES was associated with higher BMI-p < .001) and participants with a higher SES  but were not signif ica ntly associated with sex . Taking into account these demographic variables, there were no significant relations with abuse  or neglect .Hair cortisol concentrations were higher in older participants  and men compared to women . There was no association with SES . Controlling for age, sex, and SES, experiencing abuse was significantly related to hair cortisone. Higher levels of experienced abuse were related to greater cortisone concentrations . Conversely, the effect of experienced neglect was not significant .We observed higher hair cortisone levels for older participants .An indirect effect can be significant even if not all of the direct paths are significant. For completeness, we tested whether any of the indirect effects were significant, however, this was not the case , RMSEA = 0.00, and CFI = 1.00]. We found the same pattern of significant results and similar strength and direction of path coefficients. There were 76 participants who were living with their parents at the time of the data collection. The model fit for this subsample was acceptable . However, running the path model for this subgroup led to a different pattern of results with the previously significant effects of abuse on hair cortisone concentration  and BMI-z  disappearing. This might suggest an age effect but could also be the result of a lack of power in the last analysis as this group was smaller than the group of participants who were not living with their parents.A number of additional analyses were conducted to exclude alternative explanations for the findings. For one, trauma may affect individuals in a different way depending on whether it is ongoing or not. Therefore, we ran the analyses separately for participants who were still sharing a household with their parents and those who were not. Of the total sample, 173 participants were not living with their parents at the time of the data collection. Running the model in this subsample, we found good model fit  and the same pattern of significant results emerged, with similar path coefficients, suggesting that there was no suppression effect. It has also been suggested that the cortisol:cortisone ratio and the sum of cortisol and cortisone may be meaningful indicators of HPA-axis activity , RMSEA = 0.00, and CFI = 1.00; sum: X2 = 7.64 , RMSEA = 0.00, and CFI = 1.00]. Ratio was predicted by age  and SES  but not abuse or neglect. Ratio and BMI-z were also not related . The sum of cortisol and cortisone was related to age  and abuse  but not BMI-z .We initially tested the unique effects of cortisol and cortisone. Cortisol and cortisone were highly correlated. In two sensitivity analyses we tested whether cortisone suppressed the effects of cortisol and vice versa by running the analyses for cortisol and cortisone separately. In both cases the estimates of model fit were satisfactory . Physical abuse showed similar associations with the variables in the model as overall abuse did. There was a significant association with BMI-z , cortisol  and cortisone . Results were also similar for emotional abuse . Emotional abuse was associated with BMI-z , cortisol , and cortisone . The pattern of results for emotional neglect was also similar to overall neglect. Model fit was adequate . Emotional neglect was not associated with any variables of interest .Physical and emotional maltreatment might have differential effects. Therefore, we explored physical and emotional abuse, and emotional neglect in separate models. We omitted physical neglect from these analyses because on its own, physical neglect did not have sufficient variance  or internal reliability (α =.24–.64). For physical abuse, model fit was good  and did not affect the path coefficients substantially.We also ran the model again with season and medication use as control variables for hair cortisol and cortisone, respectively. This resulted in a model that fit the data adequately [z. Moreover, we observed higher concentrations of hair cortisone in individuals who had experienced abuse. However, contrary to our expectations, neither hair cortisol nor hair cortisone mediated the association between abuse and BMI-z. Neither hair cortisol nor hair cortisone had a direct effect on BMI. Moreover, neglect did not affect hair cortisol, hair cortisone, or BMI-z.This study investigated the effect of experiencing child maltreatment on BMI and the mediating role of chronic stress, indexed by hair cortisol and cortisone. Confirming previous research , 13, we In line with most previous research , 13, abuAs expected, abuse was related to increases in hair cortisone (and trend-level increases in cortisol) suggesting chronic levels of stress in individuals with abuse experiences – in some cases decades after the abuse occurred. This is also in line with the majority of research on maltreatment and hair cortisol which suggest elevated cortisol secretion . It is iEvidence of hypocortisolism has generally been interpreted in the context of the allostatic load model: over time the stress response is downregulated to maintain homeostasis. The current study found evidence of elevated cortisone levels in abused individuals—in particular in adults. However, this is not necessarily in contradiction to the allostatic load model since intra-individual cortisone levels may have been downregulated over time, but the cross-sectional nature of the study does not allow us to test this hypothesis. Collectively, these findings show that experiences of abuse get embedded in the body's physiology by reprogramming HPA-axis and higher BMI but that these might be separate processes.From a methodologic perspective, this finding also supports the measurement of hair cortisone in addition to hair cortisol. At the moment, the majority of studies focus on hair cortisol and do not include a hair cortisone measures. Cortisone levels are generally higher than cortisol levels. It has been suggested that this might make cortisone more readily detectable and a more powerful indicator of chronic stress . Effectsz. Previous research has suggested a relation between HPA-axis dysregulation and obesity but results were inconsistent  and grants of Leiden University to initiate and support the Research Profile Area Health, Prevention and the Human Life Cycle awarded to MI, P. Assendelft, and B. van Hemert.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.


What makes a literate person? What leads to literacy gains and losses within and between individuals and countries? This paper provides new evidence that helps answer these questions. The present comparative analysis of literacy is based on large representative samples from the Survey of Adult Skills conducted in 33 countries, with 25–65 year old participants. We provide, for the first time, estimates of relative importance for a comprehensive set of experiential factors, motivations, incentives, parental influence, demands of workplace, and other predictors of influence. We sketch a configuration of factors that predicts an “ideal” reader, i.e., the optimal literacy performance. Moreover, we discover a pivotal role of the age effect in predicting variability between countries. Countries with the highest literacy scores are the ones where literacy decreases with age the most strongly. We discuss this finding against current accounts of aging effects, cohort effects and others. Finally, we provide methodological recommendations for experimental studies of aging in cognitive tasks like reading. In other words, roughly one in a thousand papers produced by the entire scientific community in the last 40 years on any scholarly topic is related to issues of literacy.What makes a literate person? What leads to literacy gains and losses? These questions are at the forefront of current research in social sciences and humanities. To illustrate, a search for terms Arguably, the ultimate goal of this line of research is to answer the question: what causes gains and losses in literacy. This goal transcends national, social, cultural, and linguistic boundaries and encompasses full ranges of age, gender, ability, and clinical conditions. A material help in achieving this goal comes from recent (since mid-1990s) international surveys of basic information-processing skills like literacy, numeracy, and problem solving in adolescents and adults .The present paper focuses on the most recent and comprehensive Survey of Adult Skills. This survey was launched in 2011 under the Programme for the International Assessment of Adult Competencies (PIAAC) guided by the Organization for Economic Cooperation and Economic Development  and has Unsurprisingly, availability of PIAAC and similar surveys as data sources has generated a substantial boost in the literature on labor-market economics, sociology, education, and management . This literature establishes reading literacy as a foundational skill in a modern technological society. It describes profound economic, cultural, and social impacts of an inadequate literacy level on a person’s employability, income, well-being, health, and social engagement in the modern technological society and marketplace –9.Perhaps the most important and disturbing finding in this literature is that a large share of the adult population falls short of the literacy competency needed for skilled workers in the modern society . This is true even for developed economies and among educated populations: e.g., over 50% on average in all countries that have participated in the PIAAC Survey are functionally illiterate, over 40% in Canada, and one in four university-educated and one in two college-educated students in the province of Ontario, Canada –13.Against this background, it is surprising that cross-linguistic international literacy data from PIAAC have gone largely unnoticed in psychological and linguistic research centering on language use, cognitive development, learning, and skill acquisition . To fillThis approach deviates from the common practice of individual survey-based studies to track the impact of a small number of predictors in a restricted subset of country samples . Our apIn sum, we aim to offer new evidence on what makes a person literate across countries and languages, as well as provide some guidance to psychological research by pointing to the factors that warrant additional scrutiny and tighter experimental control in future research. Finally, we will highlight the practical implications of our findings, which may be of interest to social scientists and policy-makers.In line with several prior analyses , 24, we https://www.oecd.org/skills/piaac/onlineassessmment/demo/). The majority of participants across countries took the digital version of the literacy test. A printed version was also available to individuals uncomfortable with using computer technology: these individuals also completed a separate test of reading skill [The dependent variable of this study is literacy score. PIAAC assesses literacy in the tasks that test comprehension, evaluation and integration of words, sentences and texts in authentic information-processing contexts , 27. Somng skill , which iThe literacy scale ranges from 0 to 500 points, with the observed range across samples from 0 to 464. PIAAC has identified five discrete achievement levels for literacy, with level 3 (276–325 points) or higher deemed sufficient to operate as a skilled worker and participate in social and cultural life in the modern information-based economies [Earlier reports have identified a large number of background variables that influence the distribution of literacy scores. We begin their exposition with variables that tap into extrinsic motivation to improve one’s literacy skill , and proceed to those related to intrinsic motivation , and finally control variables , 30. TheFormal educational attainment after the mandatory schooling is known to strongly correlate with literacy levels –33. RobuA central contribution of the PIAAC survey is its scrutiny of skills in use at one’s workplace. Similar to formal education, holding a job with substantial demands for information-processing skills, including literacy, is expected to enhance an individual’s literacy level. At the same time, self-selection of prospective workers and selectivity of the marketplace may both be based on the individual’s readiness to perform at the required literacy skill level. We examine contributions of workplace literacy and learning-on-the-job by considering three PIAAC variables: an index of use of reading skills at work (READWORK) and numeracy skills at work (NUMWORK), and of the perceived amount of learning that one undergoes at work (LEARNATWORK) . NumeracLifelong learning can be pursued in a variety of ways, some involving informal education . Pursuit of informal education relies on intrinsic motivation for learning, and has also been shown to increase literacy levels, through a sustained practice of reading and understanding texts –43. We uReading for pleasure has long been identified as an important and lasting predictor of reading development and proficiency in children, adolescents and adults Broadly speaking, all independent variables listed above are at least partly related to literacy because they modulate the amount, quality, or intensity of reading practice that a person engages in. Psychological literature terms this practice as “exposure to print” and has demonstrated its positive correlation with proficiency in reading comprehension among children, adolescents and young adults of the college age –49.Importantly, exposure to print also continues to accumulate with advancing age, and as such should lead to a gradual increase in literacy. Age also comes with a continuous lifelong accumulation of knowledge as seen in vocabulary growth –53. As wAdditionally, we considered variables of demonstrated or potential importance for literacy performance. One group of controls is parental resources, i.e., an indirect index of how supportive home environment is for developing literacy skills and pursuing education. We included measures that prior literature deemed influential , 57–61: https://www.oecd.org/skills/piaac/data/). However, two national samples were removed from the analysis. First, the Russian sample did not report several variables critical for our analysis, e.g., whether an individual was born in Russia and whether an individual’s home language is the official language of this country. Second, after trimming described below, the Singapore sample was represented by too few datapoints (458), which could lead to overfitting of regression models to the data given a large number of predictors.As a source of the PIAAC data, we used the publicly available files from 35 countries  as well as individuals with missing values for education and occupational status.SD = 11) of the original sample sizes. The vast majority of removed cases were due to our age and residence/language restrictions. Sizes of the final 33 national subsamples with 25–65 y.o. adults are shown in One of the attractive features of PIAAC and similar surveys is that their samples are weighted and can be used to make inferences about populations of entire countries. This is achieved with the help of weights that enable each observed respondent to stand for a larger segment of the population. To estimate contributions of predictors to literacy scores, we used ordinary least squares regressions with Jackknife Repeated Replication weights that correct for the complex designs of PIAAC samples which vary from country to country . The appWe acknowledge that relationships between literacy and predictors that we consider present a complex network of direct, indirect and reciprocal effects, which may warrant use of sophisticated analytical techniques  and 51% (Israel) of variance, with a median of 40% (IQR 12%), see η2. This index measures a predictor’s independent contribution to explaining variance in literacy scores when variance associated with other predictors is partialled out. Partial η2 values are comparable across models and are reported jointly.We estimated effect sizes and relative importance of predictors in each model with the help of partial η2 effect-size estimates for each country, as well as the median and IQR of each effect size across all countries. Variables are presented in η2 aggregated across all countries. We further tested a large number of two-way interactions between education, age and other predictors: many of them have reached the nominal significance level (0.05) thanks to a very high number of observations, but all had negligibly small effect sizes . We do not discuss these interactions further.Tables We provided an additional and perhaps more intuitive metric of effect size: i.e., a difference in predicted literacy scores associated with extreme values of a given independent variable  divided by the country’s standard deviation in literacy scores. The resulting standardized effects are expressed in units of standard deviation and are comparable across samples. Tables 1–3 report standardized effects for each predictor per country in S1 Section of ρ = 0.72), with median correlation coefficients for specific countries ranging from ρ = 0.45 (Israel) to ρ = 0.85 (France), all ps < 0.05.We begin with the bird’s eye view of predictors of literacy by considering their contributions aggregated over the 33 national samples. Generally, all samples converged on which predictors were more influential than others. Rank-order Spearman correlations between all pairs of countries showed a high degree of agreement . A higher level of education consistently came with higher literacy scores, with the biggest step-wise score increase between the lowest (incomplete high school) and the second lowest educational levels (completed high school) in most samples, see plots in By far, the strongest effect on literacy scores in every sample was associated with formal education  was the second strongest predictor of literacy scores: The increase in literacy scores between levels of this factor was roughly linear. This finding confirms the notion that the cultural or scholarly capital of the family provides a long-lasting advantage across the entire adulthood, even when controlled for multiple other factors [The number of books in the parental household . A large amount of these intrinsically motivated activities led to higher literacy scores, with somewhat diminishing gains in the upper range of these variables, see Engagement in reading and numeracy activities at home were similarly influential  was a relatively minor contributor to literacy scores when considered across all countries. Younger individuals consistently showed higher literacy scores than their older counterparts. Importantly however, the country-specific effect sizes of age were extremely variable: the IQR of the partial η2 estimate was about 1.5 times larger (1.63) than the median. We return to this observation below.Age , with better health associated with higher literacy scores. The effect of Learning at the workplace  uncovered an interesting finding: the individuals with lower literacy levels were the ones who signalled an increased need to learn on the job. This suggests that workers have a substantial insight into their fit with the information-processing demands of the job: the demands are more challenging for those who are less literate. Readiness to learn  showed that higher levels of intrinsic motivation to pursue knowledge came with higher literacy scores as well. The volume of numeracy activities at work and, to a lesser degree, reading at work (median η2 = 0.45% and 0.34%) both boosted literacy scores, even if to a more modest degree than numeracy and reading at home (reported above).Health status also showed a relatively small effect  explained additional variance in literacy. In most countries, the highest literacy scores shown by individuals who pursue both work and education (and thus are likely ready for their distinct demands on information-processing skills), followed by—in decreasing order of mean scores—individuals who work (and are not in training), individuals who are not employed but are in job training, and those not employed and not in training. Finally, a higher level of mother’s and father’s education  contributed to explaining small amounts of variance in literacy scores. Remaining predictors  showed effect sizes below the threshold recommended by [η2 = 0.20%). We do not discuss these variables further.Several additional control factors exercised weak to moderate effects on literacy levels. Occupational status  formal education, practicing reading and numeracy at home, aging, using reading and numeracy for work, and informal education.Literacy, whether acquired through relatively short spurts of formal education, in response to workplace demands, or through home-related activities, sees gains when it is used more extensively and losses when it is not. This finding is in line with the long-established role of print exposure in literacy attainment and with the “use it or lose it” account of skill acquisition: practice makes perfect. The effect of age appears to break out from this pattern, however. While linguistic experience and knowledge are known to accumulate with age , 68, 69,Another strong group of predictors of literacy scores can be informally classified as “filters”. They codify the professional and academic achievements of individuals and their readiness to sustain the achieved level, which—to a large extent—is determined by their literacy. These predictors include formal education, occupational status, and the need to learn at work. Indeed, the very purpose of PIAAC was to evaluate how foundational skills, including literacy, shape educational and labor market opportunities in modern advanced economies. In our opinion, the factors in this group are convenient and strong markers of how fully a person has realized or is capable of realizing their academic and professional potential given their literacy level. In terms of , they meA third group of factors represents the endowment that an individual receives from their family and is labeled “parental”: it includes the number of books in the childhood household and mother’s and father’s education. The positive impact of the family cultural or scholarly capital demonstrably carries over the entire adult life: it is as strong in 25–30 year olds as it is in 61–65 year olds, as shown by non-significant interactions with age. Finally, we mention the independent, relatively minor contributions of factors that do not fall into any group: motivation to learn as a personality trait and self-reported health status.η2. Because the assignment of formal education to a specific group is ambiguous and its contribution monumental, for the purposes of this estimation we excluded this factor from both the “experiential” factors or “filters”. Under these conditions, experiential factors accounted for a median of 70.0% of total variance explained in literacy scores by all factors across samples (IQR 8.8%); filters accounted for 22.2% (IQR 6.1%); and parental factors for 50.0% of variance (IQR 10.8%). The summed amount of variance exceeds 100% because some of the variance is shared between experiental factors, filters, and parental factors and is accounted for twice when individual contributions of groups are summed up. What we conclude from this analysis, is that the group of factors related to the amount of practice that people get with literacy-related skills is the strongest determiner of their literacy level. The influence of the family  is very strong as well, when its component predictors are considered jointly. A non-trivial but the smallest amount of variance is also explained by “filters”, variables indicating one’s fit for an educational or occupational environment.To quantify contributions of each group of factors to literacy scores, we calculated the proportion of variance that each group accounts for out of the total amount of variance explained by all predictors, or each group’s In sum, the present analysis quantifies, for the first time, the relative contributions of individual predictors and groups of predictors to explaining variance in literacy scores and improves our understanding of what makes a good reader. PIAAC is a dataset geared towards population-level estimates, and statistical guidelines to using PIAAC data specifically warn against making inferences for individuals. Yet we can use the data to describe a hypothetical ideal reader. As expected, this type of reader has acquired and continues to accumulate reading experience over their lifetime from a maximally broad variety of activities . They are also the kind of person whose motivation and ability to enhance literacy is supported by the environment in which they are raised and by the genetic predispositions inherited from parents. Finally, they are a person living in an environment that provides stronger incentives and supports for reaching higher literacy levels, often in the shape of formalized qualifications required for personal, financial or social success.So far, we analyzed common factors driving literacy distributions across 33 national samples. An equally important question is whether countries show systematic differences in which predictors affect their distributions.To this end, a conditional inference tree was fitted to the ranks of national samples based on literacy scores as a dependent variable. We used literacy-based ranks rather than mean literacy scores because of skewness in the distribution of national literacy scores. The predictors used in the conditional inference tree were the same as reported in Tables η2 > 2.94, p = 0.009) were classified together: Denmark, Finland, Netherlands, Norway, Japan, South Korea and Sweden. These countries have very consistent and very high mean literacy scores . These countries also rank 1, 2, 3, 4, 6, 14 and 17 on literacy scores in the list of 33 countries. All other countries were grouped together.The resulting conditional regression tree identified age as the only relevant factor for classifying countries into dissimilar groups. Seven countries in which the effect of age was strong  than the second strongest predictor: education (η2 = 3.58%). A monotonic age-related increase in vocabulary size has reported in a web-based mega-study  [An observable effect of chronological age on any information-processing skill is in fact a conflation of counter-directed effects of multiple components. One component is a lifelong accumulation of experience with the reading skill. This accumulation is evident, for instance, in a continuous increase in vocabulary size with age. Recent lexical decision mega-studies  in Dutch and English , 72 repo 48,000) . A simil 48,000) , 24, in  48,000) , 75. For 48,000) , 77 or i 48,000) .So far, we discussed age only as an index of the amount of practice with language. Yet age is also obviously related to the psychological and physiological processes of aging that accompany maturation –81. In tA final component of observable age effect is the impact of a cohort. Forty-year-old participants in 2012 are characterized both by their age (40) and the educational and environmental experiences that differentiate their cohort (born in 1972) from others , 88. In In the present analysis of cross-sectional data, we are not able to fully break apart the observed effect of age into specific contributions of lifelong practice, skill loss due to under-use, aging, and the cohort effect. It is worth stating that the same methodological limitation is true of any experimental study that compares a group of younger and older participants. However, we provide evidence in favor of some components of the age effect. We discuss these in the following section.We also note that apparently no other predictor of literacy shows such a conflation of sources of variability as is evidence in the effect of aging. We believe this to be the reason that age was the only predictor differentiating between countries. All other predictors had a similarly strong or weak impact on literacy levels across all countries.negative correlation between age and literacy scores, after controlling for other influences. We argue that the correlation is weaker than typically recognized. Earlier reports [2 of 6% and an IQR of 8%. If education is included in the hierarchical regression model at step 1 and age at step 2, the amount of unique variance explained by age shrinks to an average of 50% of the original R2: with a range of 0–13%, a median of 3% and an IQR of 3%. We argue, however, that even this is an overestimation of the age effect. The reduction is even stronger once a larger set of predictors is considered. In a hierarchical regression model that contains all predictors listed in Analysis 1 as step 1 and age at step 2, R2 explained by age further reduces to only 20% of the original R2 value: a range of 0–5%, with a median of 1% and a mean of 1.2%. This reduction in the effect size of age is methodologically important: studies that do not control for other influences on literacy scores may inflate the effect of age by a factor of 5. Still the differences in the size of age effect between countries are presently observed even when controlling for a large number of additional factors, which warrants an investigation.The present analyses, as well as multiple prior analyses of PIAAC and similar surveys , converg reports  suggesteη2) and the mean literacy score of the country is ρ = 0.49 (p < 0.01). The relationship between effect size of age and rank literacy score for a given country is visualized in To reiterate, age proved to be a pivotal factor in classifying countries based on the effect sizes of predictors of literacy scores. The class of countries with the strongest contribution of age mostly included countries with the highest mean literacy scores. We expand this novel finding by reporting that national samples with the highest average literacy scores show a much stronger effect of age than the remainder of the samples. The Spearman’s rank-order correlation between the effect size of age . We conclude that it was not the case that the most-literate countries showed a stronger age effect because other factors  were less influential in those samples than in others.A second option may be that factors other than age may be less influential in some samples than others, leaving more variance to be explained by age. This may account for an unequal distribution of the age effect sizes across countries. Yet an analysis of unique variance explained by age with and without being corrected for the influence of other predictors rules out this possibility. Mean literacy scores of countries did not correlate with the amount of variance explained by factors other than age  effect of age may emerge in those countries where the aging and the cohort effects amplify one another. Older participants in such countries may show lower literacy skills than younger ones both because of accumulating negative consequences of maturation across adulthood and because their cohorts had fewer or lesser-quality opportunities to develop and maintain their literacy skills through education, training, or employment. Our assumption of better educational and employment opportunities for more recent birth cohorts in the countries that we classified together  agrees with their extremely high standing in the PIAAC literacy tests  and an overall positive correlation between the age effect size and mean literacy score of the country. We note that our data run counter to Barrett and Riddell’s argument , 24. In In the absence of longitudinal data, our above theorizing remains inconclusive. It does, however, lead to falsifiable predictions. We expect that longitudinal research will find (a) a broad variability in the cohort effect sizes, with stronger effects observed in the countries with more literate populations; (b) relatively similar influences on skill coming from aging, and (c) some cross-country variability in age-related effects of accumulation of knowledge and loss due to under-use, commensurate with the countries’ economic, cultural and social affordances for individuals of different age groups.The overarching goal of this project was to examine the distribution of literacy skills in a large pool of representative national samples and identify the roles of individual predictors and groups of predictors in explaining variance in literacy scores both within and across countries. The motivation was to provide a flourishing field of language research with a comprehensive chart of psychological, social, economic, and cultural factors that contribute to success or failure in meeting the literacy demands of the modern-day technological society. We also sought to establish sources of systematic variability between countries and link them to the overall literacy levels of those countries.Analysis 1 was primarily descriptive and established both the range of relevant predictors of literacy and their relative contributions to explaining variance in literacy scores both in individual countries and in aggregation. Generally, all countries were similar in the hierarchy of predictors of literacy in terms of their relative contributions . Effect sizes were reported for all predictors and all countries in Tables experiential predictors that quantify the amount of reading and related activities like numeracy at home and at work (η2 = 70%); parental predictors that tap into the cultural and scholarly capital of the individual’s childhood family (η2 = 50%); and filter predictors that codify academic and professional qualifications and one’s fit to them (η2 = 22%). We believe that our findings present a fairly complete descriptive picture of what makes people more or less literate, given the available data sources. It is worth mentioning, however, that our regression models only explained about 40% of variance in literacy scores. Thus the task of pinning down non-random variance in individual and country-wide achievements in the literacy domain is far from complete.Rich data sources from PIAAC surveys from 33 countries served as the empirical base for this project. These include literacy scores and a massive selection of variables that are comparable across countries. We restricted our analyses to the age range of 25–65 y.o. and to non-immigrant populations who spoke the language of the test as their first language. parental factors in predicting literacy  reinforces the notion that the problem of inadequate literacy in present-day adults propagates into future generations [SD in literacy scores. This is the same magnitude of difference in mean literacy scores of an average respondent with a completed high school diploma and one with a completed Master’s/PhD degree. Thus, success or failure of a nation to procure advancement in the literacy level of a current workforce have a noticeable impact both on the present and future society as well as economy.An additional finding from Analysis 1 merits a separate discussion. The strong role of erations , 92. A lAnalysis 2 examined whether variability in the country-specific distributions of literacy skills is systematic and whether it can be explained by one or more individual predictors of literacy. The systematic nature of variability was revealed in the classification analysis, which grouped together countries with the highest and very consistent literacy scores  versus countries with lower and more variable literacy scores, see ρ = 0.49, p < 0.01. That is, the better a country’s population performed in the literacy test, the more decline was observed in literacy scores as a function of age.Furthermore, Analysis 2 demonstrated for the first time that the cross-country variability in literacy achievements is at least partly related to fluctuations in the effect of age. Thus, age was a primary factor that determined classification of countries by their literacy score-based ranks, described above . This suTo interpret this finding, we reviewed and tested several components of the age effect that the literature proposed. Briefly, the effect of age is a conflation of aging  and accumulation of linguistic and other knowledge and experience over the lifetime, and possibly other factors . Thus, with age a person is more likely to experience health problems affecting cognitive performance and potentially level of literacy; this person is, however, likely to also gain experience in at least some literacy-related domains . Moreover, an age effect is confounded with a cohort effect and thus a decrease in literacy scores over time may have a true age component but also be a function of differences in the quality and quantity of education and workplace demands across different cohorts.The present cross-sectional data did not allow us to disentangle all of the components and account for which of them drove the observed impact of age. Yet our analyses allowed us to rule out some possibilities. Thus, we did not find independent evidence for the possibility that most literate countries are also the ones where the maturational effects of aging  are stronger or more common than in less literate countries. The most likely culprit for the pivotal role of age in explaining variability between countries is the cohort effect. We hypothesize that the countries which show higher literacy scores and, relatedly, a stronger negative effect of age on literacy are those countries where the cohort effect amplifies and is co-directed with the age effect. In other words, these are the countries where older individuals have poorer performance compared to other countries primarily because the more recent cohorts in these countries are trained consistently better than the less recent ones. Under our hypothesis, what comes out as a fluctuation in the size of the age effect is in fact a difference in the evolution of the educational, social and economic systems, which led to a more substantial incremental improvement in literacy skills of more recent cohorts and to greater overall literacy levels in some countries but less so in others. We note that our findings run counter to the those of who used multiple surveys to create synthetic cohorts and observed a cohort effect that amplifies the age effect in some of the most literate countries but attenuates the age effect in others (see above for detail) , 24. LonWe supplement our findings with a few methodological recommendations and pointers to future directions of research. First, one of the strongest individual predictors of literacy across countries was the number of books at one’s childhood’s household. The PIAAC entry for the question reads: “About how many books were there in your home when you were 16 years old? Do not include magazines, newspapers or schoolbooks. To give an estimation, one meter of shelving is about 40 books.” and has the following possible answers: 10 books or less, 11–25, 26–100, 101–200; 201–500; more than 500 books; and don’t know. Given the brevity of administering this question, we suggest routinely collecting this information in all reading experiments on adults and including its outcome as a co-variate of reading performance.Second, despite the wealth of literature supporting its importance for literacy development (see references above), informal education proved to have negligible impact on literacy skill. We speculate that this weak effect is either because the PIAAC questionnaire only asks whether this education was pursued in the last 12 months and misses its long-term impact, or the impact of non-formal education is absorbed by other, more influential variables . This suggests that future surveys may consider a scrutiny of non-formal education on a longer timescale.Third, the cross-country variability in the size of the age effect suggests that results of experimental studies on aging effects on reading, literacy, numeracy and related skills in adults are not readily comparable across countries. For instance, while Canada, UK and USA demonstrate a low impact of age on literacy, several Nordic countries as well as Japan show a markedly stronger impact. In this setup, a typical experiment that compares young adults (20–25 y.o.) to older adults (65+ y.o.) in a language related task would uncover stronger effects in the Finnish or Dutch sample than in the Canadian or American one. This age × country interaction would likely be spurious and would reflect differences in the cohort effect that cannot be accounted for in a cross-sectional study. In addition, to correctly estimate the effect of age both in within- and between-countries studies, it is important to include other relevant predictors of literacy and reading performance . In the absence of such predictors, the effect of age tends to be greatly inflated. As shown above, the effect of age on literacy reduced to 50% of the original effect size when controlling for education and to as little as 20% of the original when controlling for other predictors.Fourth, the present data point to a consistent negative effect of age on literacy. This effect runs counter to the well-established positive effect of age on vocabulary growth , 68, 76 We also note as a limitation that immigrant groups were excluded from the current cross-national study, because of the well-known rampant variability in the number and social, educational, and demographic characteristics of respective populations in different countries  –96. We bS1 File(PDF)Click here for additional data file.


Purpose This systematic review investigates the effectiveness of workplace interventions to rehabilitate musculoskeletal disorders (MSDs) among employees with physically demanding work. Methods A systematic search was conducted in bibliographic databases including PubMed and Web of Science Core Collection for English articles published from 1998 to 2018. The PICO strategy guided the assessment of study relevance and the bibliographical search for randomized controlled trials (RCTs) and non-RCTs in which (1) participants were adult workers with physically demanding work and MSD , (2) interventions were initiated and/or carried out at the workplace, (3) a comparison group was included, and (4) a measure of MSD was reported . The quality assessment and evidence synthesis adhered to the guidelines developed by the Institute for Work & Health  focusing on developing practical recommendations for stakeholders. Relevant stakeholders were engaged in the review process. Results Level of evidence from 54 high and medium quality studies showed moderate evidence of a positive effect of physical exercise. Within this domain, there was strong evidence of a positive effect of workplace strength training. There was limited evidence for ergonomics and strong evidence for no benefit of participatory ergonomics, multifaceted interventions, and stress management. No intervention domains were associated with “negative effects”. Conclusions The evidence synthesis recommends that implementing strength training at the workplace can reduce MSD among workers with physically demanding work. In regard to workplace ergonomics, there was not enough evidence from the scientific literature to guide current practices. Based on the scientific literature, participatory ergonomics and multifaceted workplace interventions seem to have no beneficial effect on reducing MSD among this group of workers. As these interventional domains were very heterogeneous, it should also be recognized that general conclusions about their effectiveness should be done with care.Systematic review registration PROSPERO CRD42018116752(https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=116752). Although there has been a major focus on rehabilitating musculoskeletal disorders (MSDs), it remains a significant problem in many workplaces around the world. Data from the Working Environment and Health study, representing the general working population in Denmark, show that the proportion with musculoskeletal pain several times a week has increased from 31% in 2012 to 33% in 2018 –7. MSDs Risk factors and effective solutions for MSDs vary from industry to industry (i.e. group of companies or workplaces that are related based on their primary business activities), and especially between workplaces constituting physical or sedentary labour. Therefore, it is recommended that individual workplaces address the risk factors that are most important to them and chose solutions applicable to their work context . CompareCurrently, there are no known published systematic reviews documenting and summarising the literature on the effect of workplace-based interventions specifically for workers with MSD and physically demanding employment. Previous systematic reviews within this topic have mainly focused on MSD in one body region among either the general working population  or among a specific job group . A systematic review by Van Hoof et al.  only fouPrevious reviews have dealt with this methodological challenge by including both RCTs and non-RCTs. To further increase the relevance for practice, these reviews have also employed the quality assessment and evidence synthesis developed by the Institute for Work & Health  which focuses on the development of practical guidelines for stakeholders. In such a review process, Van Eerd et al.  investigThe aim of this systematic review is to investigate the effectiveness of workplace interventions to rehabilitate musculoskeletal disorders among employees with physically demanding work. Workplace interventions are here defined as interventions that are initiated by the workplace, supported by the workplace, and/or carried out at the workplace. Level of evidence will be synthesized within several broad intervention domains such as physical exercise, ergonomics, participatory ergonomics, and multifaceted interventions. If possible, due to a data-driven approach, each domain will further be divided into more specific intervention categories. Based on the evidence synthesis, practical messages for stakeholders will be developed. To introduce a more practical approach, relevant stakeholders are engaged in the review process and both RCTs and non-RCTs are eligible for inclusion.This systematic review followed the ‘Preferred Reporting Items for Systematic reviews and Meta-Analyses’ (PRISMA) guidelines for reporting systematic reviews and the IWH guideline for workplace-based interventions. Inspired by the IWH Systematic Review Programme , relevanThe review has been registered in the International Prospective Register of Systematic Reviews (PROSPERO) number CRD42018116752 and a protocol paper has previously been published .Eligibility criteria can be seen in Table The systematic search was conducted in the following bibliographic databases: PubMed (including the database ‘MEDLINE’) and Web of Science Core Collection . The search strategy consisted of combining the following four main components: (1) musculoskeletal diseases/disorder AND (2) workers AND (3) workplace intervention AND (4) date (published within the last 20 years: from 1998 to 2018). The search strategy for each database has previously been reported [The PRISMA flow-diagram illustrated in Fig. For each included study, systematic data extraction was employed to collect the following general characteristics: (1) author year and country, (2) study design, (3) study population, (4) intervention and comparison, (5) number of participants, (6) time-frames of outcome measurement, (7) results, and (8) quality appraisal.Since MSDs are a diverse group of conditions, several different outcome measures have been employed in the literature. Thus, we decided not to exclude potential relevant studies due to heterogeneity in outcomes, as long as they represented a measure related to MSD. The outcomes employed for the quality appraisal and evidence synthesis, therefore, included any change in musculoskeletal pain, symptoms, prevalence or discomfort from baseline to follow-up (see the PICO illustrated in Table Two authors (ES and KVGS) independently assessed the quality of each study and any disagreements were discussed with the senior author (LLA) until a consensus was reached. For the methodological appraisal, we used the quality assessment methods developed by the IWH consisting of 16 unique questions , or at least ¾ of all the studies within a specific intervention category or domain (explained below) had to have the same direction of effect , 23. ThiLevel of evidence was synthesized for high and medium quality studies within the following 5 broad intervention domains agreed on by the authors: physical exercise, ergonomics, participatory ergonomics, stress management, and multifaceted. If deemed possible by the authors, due to both a practical and a data-driven approach, each domain was further divided into relevant intervention categories. For instance, the domain of physical exercise was divided into strength training at the workplace, aerobic training at the workplace, and stretching at the workplace. This allowed for a more specific and stakeholder-friendly evidence synthesis. When consensus was reached by the review team on the intervention domains and categories, evidence was synthesized for each domain and category.The bibliographic searches identified 15,556 articles, of which 3091 were duplicates. Of the 12,465 remaining articles, 12,113 were excluded in the abstract screening as they did not meet our eligibility criteria. Of the 352 full-text articles retrieved, 221 met the overall inclusion criteria. Since the aim of this review was to investigate the effectiveness of interventions for workers with physically demanding work, we only included the articles describing this population (n = 78). The remaining articles (143) will be reported in a separate paper, reporting the effectiveness of interventions for workers with sedentary employment.In addition to the 78 articles identified for this review, 4 articles were sent to the review team by colleagues, which were published after the systematic search was carried out. In, total 82 papers were included in the review. 19 of these 82 articles reported different outcome measures (i.e. primary or secondary outcome measures not related to MSD) of a unique interventional study , 20 studies were medium quality (50–85% of criteria met) and 9 studies were low quality (< 50% of criteria met). Only high and medium quality studies were eligible for the evidence synthesis whereas the summary table only describes these studies , with a further 6 performed in Norway, 5 in the Netherlands, 3 in the US, 3 in Italy, 3 in Japan, 2 in Sweden, 2 in Canada, 2 in France, 1 in Iran, 1 in Israel, 1 in Hungary, 1 in Belgium, 1 in Chile, 1 in Finland, 1 in Hong-Kong (China), 1 in Korea, 1 in Switzerland, and 1 in Turkey.The interventions across the 54 studies were grouped into 5 intervention domains: physical exercise (n = 20), ergonomics (n = 13), participatory ergonomics (n = 5), multifaceted (n = 15) and stress management (n = 3). Within these domains, 3 interventional categories were further established, based on a practical and data-driven approach by the review-team: strength training , aerobic training (including aerobic training/exercise and soccer) and stretching . Four studies did not match any of the intervention domains and are therefore discussed separately  , reduced54 suitable high or moderate quality studies were found reporting on the effect of 69 unique workplace interventions, serving as a solid foundation for the evidence synthesis and the subsequent recommendations for practitioners. There was moderate evidence of a positive effect of the domain of physical exercise at the workplace to reduce MSD among workers with physically demanding work. Within this domain, there was strong evidence of a positive effect of workplace strength training, where all 9 studies pointed in the same direction. There was limited evidence for the domain of ergonomics and thereby not enough evidence to guide current practices. There was strong evidence for no benefit for the domain of participatory ergonomics, multifaceted interventions, and stress management. The remaining single-domain intervention categories  only had one study each, and thereby not enough evidence to guide current practices. Importantly, no intervention domains were associated with "negative effects".16 of 23 interventions supported the domain of workplace physical exercise, resulting in a moderate level of evidence. Previous reviews have found evidence for the use of workplace exercise (not specified) for workers with upper limb, neck or back conditions/pain , 78 wherThe many studies within the domain of physical exercise allowed for a further categorization into strength training, aerobic training, and stretching. All of the studies within the category of strength training showed an effect on MSD and therefore led to a strong level of evidence for a positive effect. These findings seemed to be consistent for both care/hospital workers and industry/manufacturing workers. A limited level of evidence was also found for aerobic training, whereas the studies on stretching showed mixed results. This is somewhat in line with previous reviews performed on the general working population or office workers. Van Eerd et al.  found stIn spite of this strong evidence, recent numbers from the Working Environment and Health study in Denmark shows that less than a third of Danish workers are offered physical exercise at the workplace . Thus, f10 of 15 interventions showed no positive effect of workplace ergonomics on MSD leading to a limited level of evidence for no benefit for the domain of ergonomics: not enough evidence from the scientific literature to guide current policies/practices. Previous reviews on the general working population have both reported an effect, no effect and conflicting results of workplace ergonomics on MSD. Hoosain et al.  found poParticipatory ergonomics means actively involving workers in developing and implementing workplace changes which will improve productivity and reduce risks to safety and health . This is13 of 16 interventions from high or medium quality studies showed no effect of multifaceted workplace-interventions on MSD among workers with physically demanding employment. This resulted in a strong evidence level for no benefit for the domain of multifaceted interventions. In line with this, Van Hoof et al.  found ve3 of 3 interventions from high or medium quality studies showed no effect of stress management leading to a strong level of evidence for no benefit for this interventional domain. This is in line with previous reviews on upper limb and back pain among the general working population and among nurses , 14, 17.The prevention of MSDs at workplaces is a challenge and practitioners have therefore specifically asked for an evidence-based approach to better identify and implement effective interventions for employees with physically demanding work. In addition, implementing evidence-based initiatives at workplaces is a well-known challenge that may be due to the fact that existing knowledge is not conveyed clearly enough to the users, including the workplaces. Likewise, it is nearly an impossible task for OSH practitioners to find, read and synthesize relevant scientific literature on effective workplace solutions to reduce MSD. Employing the IWH review guidelines for the review provided us with the opportunity to develop relevant recommendations for practitioners. The involvement of relevant stakeholders in some of the review-steps has also maximized the practical relevance of the review and increased the opportunity for the evidence-based knowledge to reach relevant users –89. By pThe perception of musculoskeletal pain and symptoms constitutes a complex interaction of both biological, psychological and social factors , 90. MSDImportantly, length to the latest time-frame of outcome measurement (i.e. study duration) varied between studies included in the different interventional domains. For instance, the average time to the latest outcome measurement was 19.6 weeks for interventions within the domain of physical exercise, whereas it was 42 weeks for ergonomics interventions, 41 weeks for participatory ergonomics interventions, and 31 weeks for multifaceted interventions. This could have influenced the present results and it also seems to highlight the need for investigating long-term effects of physical exercise at the workplace. Whether the present findings reflect a ceiling effect of the intervention effects after a short time-frame or a gradually diminishing adherence to the intervention occurs with time—and thereby limits further improvements—cannot be elucidated based on the information available in the included studies.The interventional effect from the included studies was classified as positive if the study reported positive results on MSD-related outcomes such as pain, the prevalence of MSD/pain, symptoms, or discomfort. It should, however, be noted, that the effect was not necessarily based on the primary outcome results, but could also reflect secondary or tertiary outcome measures. As an example, in the included study by Brandt et al.  the primWe found strong evidence for no benefit of participatory ergonomics and multifaceted interventions at the workplace. Importantly, within these domains , the interventional components were so different and our data-driven approach did not allow to further divide them into meaningful categories. There may have been many factors that could have contributed to the lack of effectiveness seen in some of these studies. Workplace interventions are complex and many factors can influence how the intervention was implemented, which in turn contributes to how effective they are. As mentioned above, the timeframe for outcome measurements could be an important factor because working conditions—although modifiable—can take a long time to modify due to the length of time required to implement new policies, practices or programs. Further, MSD is a complex outcome measure and it can take time to see any meaningful change. Importantly, every organization is different and interventions need to fit the company/workplace , which cAs expected, substantial heterogeneity in the interventional outcome measures, study designs, and workplace contexts did not allow for the conduction of a meta-analysis. Specifically, outcome characteristics such as pain intensity, the prevalence of pain, symptoms, and discomfort were too broad to be matched or pooled and therefore lacked the comparability for a meaningful meta-analysis. This is also coherent with other reviews within the field of work-related interventions to reduce MSDs , 17, 23.Including both RCTs and non-RCTs in the systematic review can both be considered a limitation and a strength. Including non-RCTs may downgrade the validity and strength of our systematic review and the risk of bias will become higher in the blinding and sequence generation domains. Therefore, we employ the IWH approach for the quality assessment and subsequent best evidence synthesis that are developed to handle other study designs than RCTs. Even though RCTs are considered the most powerful experimental design in clinical trials , solely Even though the IWH approach for the quality assessment and subsequent best evidence synthesis are developed to handle other study designs than RCTs, RCTs will, in general, have the possibility to obtain a higher quality score and have a higher impact on the level of evidence than non-RCTs. This is especially because some of the questions in the quality assessment form Table  relates A strength of the study is the involvement of relevant stakeholders in the review process, which ensured a high level of practical relevance. Stakeholder involvement in the design and search strategy phases introduced a more practical approach that allowed practitioners to share their knowledge and experience from practice along with their needs in regard to developing suitable workplace solutions.Another strength is that authors were contacted to clarify whether potentially included studies were workplace-based if doubt about the location of the intervention existed based on the full-text reading. This led to the inclusion of several studies that otherwise would have been excluded for the review. Hence, this strengthens the foundation for the evidence synthesis.Even though the included studies were from 19 different countries, differences in regard to the geographical distribution of studies clearly existed. Of the 54 studies included in the review, 27 studies were from Scandinavian countries  and only 13 studies were performed outside Europe. The present study results therefore mainly reflect the effectiveness of interventions in workplaces with physically demanding work in Europe and especially in the Scandinavian countries.Publication bias cannot be ruled out from the present review. We attempted to be as inclusive as possible, as we expected that there weren’t that many eligible studies on workplace interventions to reduce MSD among employees with physically demanding work. Thus, studies with positive results were possibly more likely to be eligible for the present review. Even though the English language is generally perceived to be the universal language of science—also in regard to research within the field of work environment and health—only including these studies could have biased the present results by not representing all of the evidence available. Thus, the presence of a language restriction bias in the present study cannot be ruled out.The systematic search revealed 54 suitable high or moderate quality workplace-studies (36 RCTs and 18 non-RCTs) that focused on MSD among workers with physically demanding employment, which served as a solid foundation for the evidence synthesis and the subsequent recommendations for practitioners. The evidence synthesis recommends that implementing strength training at the workplace can reduce MSD among workers with physically demanding employment. In regard to workplace ergonomics, there was not enough evidence from the scientific literature to guide current practices. Based on the scientific literature, participatory ergonomics and multifaceted workplace interventions seem to have no beneficial effect on reducing MSD among this group of workers. As these interventional domains were very heterogeneous, it should also be recognized that general conclusions about their effectiveness should be done with care.


The role of livestock in supporting human well-being is contentious, with different perceptions leading to polarised opinions. There is increasing concern about the health and environmental impacts of a high rate of consumption of livestock products in high-income countries. These concerns are heightened by an increase in consumption in middle-income countries. On the other hand, livestock support the livelihoods of many people, particularly in low income countries. The benefits of livestock for poor livestock keepers are multiple, including the important role livestock play in supporting crop production in mixed systems, in supplying nutrients and income, and in fulfilling cultural roles. In addition livestock can provide resilience against economic and climate shocks. In view of these apparent positive and negative impacts, the role of livestock in human wellbeing is highly contested, with arguments ‘for’ or ‘against’ sometimes distorted by vested interests or misinterpretation of evidence. The Livestock Fact Check project, undertaken by the Livestock Data for Decisions community of practice, has investigated several ideas concerning livestock commonly taken as ‘fact’. By exploring the provenance of these ‘facts’ we highlight their importance and the risks of both misinterpreting them or using them out of context. Despite the diversity of the livestock sector resulting in equally diverse viewpoints, the project calls for participants in the livestock discourse to adopt a nuanced appreciation of global livestock systems. Judgement of livestock's role in global sustainable diets should be based on clear and well-interpreted information. •Livestock farming is a contentious and polarised subject in sustainable diet discourse.•Livestock facts are used to support rationales from a variety of positions.•Many ‘facts’ are used without acknowledgement of their provenance or without suitable interpretation.•Knowing what is uncertain or variable is important for fair interpretation, dialogue and rational decisions.•Transparency of evidence related to livestock is the ambition of the Livestock Data for Decisions community of practice. Since lIn livestock science, as with any scientific discipline, there are a minority of experts amongst a majority population of non-experts; both access evidence relevant to their situations and choices . It is iPerceptions and opinions of the global livestock sector are not only diverse but are also becoming increasingly polarised . For insLivestock Data for Decisions (LD4D) is a community of practice, with members from academia, NGOs, donor agencies and industry. LD4D's aim is to ‘drive informed livestock decision-making through better use of existing data and analyses’ . This mu2The livestock ‘facts’ investigated by LD4D refer both to quantitative evidence, such as a specific percentage or quantity, and to qualitative evidence, such as a broad perception or understanding. The ’facts' to be investigated were identified by a multidisciplinary working group representing the broader multi-discplinary LD4D community of practice. To help promote constructive community dialogue, efforts were made to select ‘facts’ that represented key aspects of livestock production . While the methodologies used to investigate each ‘fact’ were variable, efforts were made in every case to identify the origins of the ‘facts’ through interrogations of the relevant literature. The ‘facts’ investigated are summarised in the following sections.2.1the case for investment in the livestock sector as a basis for reducing rural poverty’ (correspondence on the Gini coefficient” from the World Resources Institute in 1996 (no further information was available relating to this correspondence). Consequently, the regularly quoted ‘one billion’ statistic is based on a calculation using previous publications and statistics, all more than 20 years old. Between 1999 and 2017, the global human population has grown from 6.1 to 7.6 billion  . This 402.4Zoonotic diseases are those transmitted between humans and animals. The control of livestock disease to benefit humans is encouraged using ‘facts’ such as ‘60% of human pathogens are zoonotic, and 75% of emerged human epidemics are of animal origin’ . These fone quarter of the animals owned by poor livestock keepers die from preventable and treatable diseases’ . Those advocating investment to improve animal health commonly state that ‘iseases’ . This ‘fiseases’ . Firstlyiseases’ . Initialiseases’ . Then, diseases’ ; a, exteiseases’ . In someiseases’ . As a reiseases’  and the iseases’  are enco2.5The various negative environmental impacts of livestock production are well recognised; with global scale ‘facts’ relating to water consumption and pollution, land use changes, biodiversity losses and greenhouse gas emissions. These ‘facts’ are often used as headlines, with a mandate to reduce the consumption of livestock sourced foods in high income countries e.g. . For ins3It is evident that many livestock ‘facts’ inherently relate to complex systems; which, to enable comprehension rely on systems modelling. There are important considerations to make when simplifying reality in this way. As discussed in previous sections, the quality, availability and resolution of livestock data will determine how closely modelled results illustrate reality. In addition modelled results are dependent on the scope and assumptions included, as well as the metrics selected to report results. The same production system could be investigated with different models reporting different metrics, producing results that are varied in their illustration of reality . For insScience deals with uncertainty and variability and therefore cannot provide unqualified solutions to problems . Global To enable an assessment of a ‘facts’ fitness-for-purpose  one must understand its provenance; this relies on effective and appropriate referencing within communications. However, this Livestock Fact Check project highlighted that many livestock ‘facts’ are communicated without following this principle. Understandably, there are trade-offs between timely consumable scientific communication and traditional scientific principles. Nonetheless care should be taken to avoid assuming the accuracy of received information or interpretations before passing them on. For instance, a single interpretation  can be magnified by repeated reference to secondary sources (making it appear that the interpretation was reached by multiple parties) rather than investigating the original single source .Livestock data in general is challenging; data collection and reporting is often ad-hoc and inconsistent, with livestock often grouped in a broad category of agriculture . ConsequTo some extent, the ‘facts’ accepted by the broader population of non-experts will not be based on their quality or the quality of their communication. It is recognised that individuals are more likely to accept facts if they align with the values they hold or reinforce predispositions . For ins4This LD4D project investigated several popular conceptions of livestock production, regularly taken as ‘fact’, with the objective of ensuring discussions, decisions and rationales are well founded on appropriate research-based information. Several key messages became apparent during the project. Firstly and not uniquely for livestock science, to maintain clarity and context, communicators (in particular scientists) should make every effort to understand primary sources for information they wish to use (and cite them appropriately). It can then be clear how old, how accurate or how comprehensive the evidence is on which ‘facts’ and subsequent perceptions are based. The livestock community then needs to decide which ‘facts’ warrant recalculation or further investigation, presumably focusing on those that cause the most polarisation. To avoid misleading or inappropriate interpretations and use of ‘facts’, scientists need to remain clear and transparent about both uncertainties and variability in livestock production at both local and global scales. The application of scientific information outside the science community is to some extent uncontrollable; nevertheless, the livestock community must remain broadly objective and balanced in presenting information about global livestock production and both its future role in sustainable diets and impacts on broader sustainable development goals.Authors declare no conflict of interest.


The importance of using evidence in decision-making is frequently highlighted in policy reports and scientific papers. However, subjective judgments of the reliability of environmental evidence vary widely, and large-scale systematic searches for evidence are only common for climate-related topics. In the medical field, evidence-based guidelines are routinely used to guide treatments. In the management of multiple-use landscapes similar guidelines could substantially narrow the science-practice gap but are largely absent. The challenges potential guidelines face are therefore unknown. For the case of forest conservation, we conducted 14 semistructured interviews with mainly forest practitioners and presented them an example medical guideline together with evidence-based statements on forest conservation (hereinafter: statement paper). We identified 28 concerns related to potential evidence-based guidelines in forest conservation. The interviews yielded approximately three major findings. First, recommendations on forest conservation are better accepted if they include clear instructions and are formulated for a specific context. Fragmentary conservation evidence complicates the formulation of specific recommendations. Second, the level of evidence framework, which indicates the strength of the available evidence, is perceived as too complex. Third, neglecting forest multifunctionality in a potential guideline hampers its application but, if addressed, potentially weakens its ecological relevance. We show that major concerns about potential evidence-based conservation guidelines are similar to the challenges experienced by medical guidelines. We also identify concerns unique to forestry. The importance of evidence-based policy-making is emphasized in countries around the globe  to different stakeholders  are well studied in health care  administration , three scientists doing more applied research and two private forest owners living and working in Germany, Switzerland, and Poland  per hectare (ha) of dead wood shall be retained in European forests. The statement in Table Similar to the medical guidelines, in the statement paper, the confidence in the available literature was expressed as LoE ranging from one to four  and a memo (which summarized the main content) were written to help us remember the context of the interviews and interpret the content A majority of the interviewees (11) detected a lack of specificity in our presented statement paper about dead-wood retention. There was a wish for more detailed information regarding the influences of climate , forest types , and accessibility  on how to retain dead wood. Furthermore, according to the majority of interviewees (eight persons), the instructions included in a potential guideline in forest conservation should be as detailed as possible. Similar to a standard operation procedure, such instructions preferably should include clearly defined management goals and state which forest operations should be carried out, as well as when, where, and how they should be carried out, to conserve biodiversity. The same persons who wished for more detailed descriptions about how scientific findings apply to their local context frequently also brought forward serious doubts about the external validity of studies conducted in other contexts  and sometimes questioned the acceptance of low recommendation grades (which can be a consequence of very specific recommendations). It was suggested in one interview that this poses a major challenge for a scientist who is asked for recommendations  also occur on a table in the backyard with a few fruit trees and no other wood.The dilemma of giving evidence-based recommendations that also apply under particular circumstances was further illustrated by the same interviewee cited above, who suggested that it is difficult to convince everyone of the validity of the currently widely cited threshold of 30 m“The practitioner [referring to state district foresters] says I need a short and precise instruction; the rest is not at all of interest for me. I don’t care if this is now LoE one or two. Besides, we know it better anyways. ... Terms like ‘level of evidence’, ‘grade of recommendation’, these are STRANGE words, these are completely strange terms, which you also had to arduously explain to me. Explain this to a thousand district foresters who are all saying, ‘Actually, I should urgently make timber now.’” (I2)In almost 50% of the interviews, it was mentioned that the level of evidence is too complex as a measure of reliability. One interviewee stated that his own traditional knowledge and experience are placed too low in the evidence hierarchy. Three more persons hinted in the same direction by emphasizing the importance of knowledge gained through experience. One interviewee who was experienced in the formulation of management concepts expressed the concern that the burden of making the right management decisions is passed down to the lowest level (district forester) if LoEs are provided. Instead, people at higher levels  should take more responsibility in formulating recommendations that the end user can trust without being familiar with the LoE framework. Another interviewee who was experienced in the development of management concepts supported this:However, in general, forest practitioners  showed interest in scientific findings and in understanding why anecdotes not supported by representative data were placed low in the evidence hierarchy.Concerns related to forest multifunctionality Several interviewees also suggested taking into account the production function of forests, which would be reduced by standing or lying dead wood because of access limitations for large machines . Furthermore, it was emphasized strongly in two interviews that dead wood retained in the forest is lost for timber production. It was illustrated by one interviewee that current handbooks and concepts often follow a segregated approach that emphasizes biodiversity conservation but neglects forest multifunctionality :In addition, the lack of compensation mechanisms, especially the importance of appreciation in terms of money, could limit the application of a potential guideline (eight interviews).Recommendations were questioned in general  in two interviews. Four interviewees raised concerns relating to visual appearance, categories used, and complexity. Furthermore, it was stated that most decision makers would suffer from information overload. Therefore, an intuitive presentation of the recommendations There exists an evidence deficit until scientists answer questions from practitioners. Such a deficit can limit trust in potential evidence-based guidelines. It may be that scientific evidence seemingly supports prevailing paradigms, which are overcome at a later point in time:Another interviewee described how recent scientific findings  have also been described in the medical literature . The patient version of our example medical guideline limits itself to recommendations  between the two completely different scientific fields in retrospect justifies our methodology to present a statement paper and a medical guideline at the beginning of the interviews.In addition to confirming common obstacles of evidence-based medical guidelines for forest conservation Fig. , we alsoA main argument against the use of medical guidelines was that it reduces professional freedom  should provide locally adapted recommendations that are written in plain language and intuitively structured  to reduce complexity. However, to keep the development of evidence-based guidelines as transparent as possible, we suggest making the LoE (upon which the recommendations are based) available to the public in an open database.Third, to better address the social dimension that brings in mainly landscape multifunctionality related concerns, we propose to first form a commission that is shielded from influential stakeholder interests. The commission could be part of a nonprofit organization , which takes responsibility for the development of evidence-based forest conservation guidelines. Akin to the formulation of medical guidelines, members of the commission  would then present preformulated recommendations to a wider group of stakeholders  to assess their strength of support  indicates that such guidelines have potential for the management of multifunctional landscapes. Further identified concerns about low specificity and high complexity were also described in medical studies. In contrast to medicine, we detected a wish of forest practitioners for more detailed but concise instructions. The emphasis on existing hierarchical structures that will frame the development of evidence-based guidelines and the high diversity of stakeholders were also unique to forest management. However, we did not find concerns that would make the development or application of evidence-based guidelines in the management of multiple-use landscapes fundamentally impossible. Therefore, we suggest conducting further research into the possibilities of this new evidence-based approach.Online resource 1Online resource 2Online resource 3Online resource 4