[Articles] Occupational physical activity and longevity in working men and women in Norway: a prospective cohort study

SummaryBackground

Studies suggest that high occupational physical activity increases mortality risk. However, it is unclear whether this association is causal or can be explained by a complex network of socioeconomic and behavioural factors. We aimed to examine the association between occupational physical activity and longevity, taking a complex network of confounding variables into account.

Methods

In this prospective cohort study, we linked data from Norwegian population-based health examination surveys, covering all parts of Norway with data from the National Population and Housing Censuses and the Norwegian Cause of Death Registry. 437 378 participants (aged 18–65 years; 48·7% men) self-reported occupational physical activity (mutually exclusive groups: sedentary, walking, walking and lifting, and heavy labour) and were followed up from study entry (between February, 1974, and November, 2002) to death or end of follow-up on Dec 31, 2018, whichever came first. We estimated differences in survival time (death from all causes, cardiovascular disease, and cancer) between occupational physical activity categories using flexible parametric survival models adjusted for confounding factors.

Findings

During a median of 28 years (IQR 25–31) from study entry to the end of follow-up, 74 203 (17·0%) of the participants died (all-cause mortality), of which 20 111 (27·1%) of the deaths were due to cardiovascular disease and 29 886 (40·3%) were due to cancer. Crude modelling indicated shorter mean survival times among men in physically active occupations than in those with sedentary occupations. However, this finding was reversed following adjustment for confounding factors (birth cohort, education, income, ethnicity, prevalent cardiovascular disease, smoking, leisure-time physical activity, body-mass index), with estimates suggesting that men in occupations characterised by walking, walking and lifting, and heavy labour had life expectancies equivalent to 0·4 (95% CI −0·1 to 1·0), 0·8 (0·3 to 1·3), and 1·7 (1·2 to 2·3) years longer, respectively, than men in the sedentary referent category. Results for mortality from cardiovascular disease and cancer showed a similar pattern. No clear differences in survival times were observed between occupational physical activity groups in women.

Interpretation

Our results suggest that moderate to high occupational physical activity contributes to longevity in men. However, occupational physical activity does not seem to affect longevity in women. These results might inform future physical activity guidelines for public health.

Funding

The Norwegian Research Council (grant number 249932/F20).

IntroductionSeminal work almost 70 years ago suggested lower risks of coronary heart disease and mortality in men with high occupational physical activity than in those with less physically demanding work tasks.Morris JN Heady JA Raffle PA Roberts CG Parks JW Coronary heart-disease and physical activity of work. In the following decades, technological advances and mechanisation reduced the need for manual labour, and the contribution of energy expenditure from work to total energy expenditure decreased.Time use and physical activity: a shift away from movement across the globe. Subsequently, since the 1990s, research has emphasised examining the association between leisure-time physical activity (LTPA) and health outcomes. Results from large prospective studies done in men, women, ethnically diverse populations, and samples from countries at varying income levels, and adjusted for confounding factors, have consistently shown an inverse dose–response association between physical activity and risk of death.Ekelund U Dalene KE Tarp J Lee IM Physical activity and mortality: what is the dose response and how big is the effect?. Combined with results from randomised controlled intervention studies,Exercise training for blood pressure: a systematic review and meta-analysis. the effect of physical activity on morbidity and longevity is now widely recognised, and its importance is emphasised through national and international guidelines on physical activity, such as those recently revised in the USA (2018) and UK (2019), and by WHO (2020).Bull FC Al-Ansari SS Biddle S et al.World Health Organization 2020 guidelines on physical activity and sedentary behaviour.However, several studies have challenged whether occupational physical activity actually conveys health benefits, and a meta-analysis suggested an 18% higher risk of all-cause mortality in men with high occupational physical activity than in those with low activity.Coenen P Huysmans MA Holtermann A et al.Do highly physically active workers die early? A systematic review with meta-analysis of data from 193 696 participants. Although these results might be explained by heterogeneity in the classification of occupational physical activity and residual confounding from socioeconomic factors (eg, education and income) and socially graded health behaviours (eg, smoking),Is there a ‘recent occupational paradox’ where highly active physically active workers die early? Or are there failures in some study methods?. mechanisms have been hypothesised supporting detrimental associations between occupational physical activity and mortality from cardiovascular disease.Holtermann A Krause N van der Beek AJ Straker L The physical activity paradox: six reasons why occupational physical activity (OPA) does not confer the cardiovascular health benefits that leisure time physical activity does. However, others argue that there is no compelling biological evidence that LTPA and occupational physical activity have opposite effects on mortality.Wade KH Richmond RC Davey Smith G Physical activity and longevity: how to move closer to causal inference. Therefore, it can be hypothesised that, if the association between physical activity and mortality is truly causal, associations between physical activity from different domains and mortality are similar when confounding is taken into account.Wade KH Richmond RC Davey Smith G Physical activity and longevity: how to move closer to causal inference. Nonetheless, if occupational physical activity per se does increase the risk of premature mortality, this would have implications for public health policy and work safety regulation.Research in context

Evidence before this study

Compelling evidence from a combination of large, prospective cohort studies and randomised controlled trials showed that physical activity might reduce the risks of many non-communicable diseases and premature mortality. We searched PubMed and Google Scholar from database inception to Jan 31, 2020, for articles using the terms “physical activity”, “occupation”, “mortality”, “cardiovascular disease”, and “cancer”, finding at least 25 studies published over the past decade that questioned whether occupational physical activity conveyed health benefits. A 2018 systematic review and meta-analysis observed that men with high occupational physical activity had an 18% higher risk of all-cause mortality than did men in sedentary occupations, supporting a so-called physical activity paradox. If causal, this finding would have large implications for future physical activity guidelines and work safety regulations. However, it is unclear whether the higher mortality risks observed are caused by high occupational physical activity per se or by a complex network of socioeconomic and behavioural factors associated with occupations involving a high level of physical activity.

Added value of this study

This study extends previous meta-analyses by use of nationally representative, harmonised data on occupational physical activity in 437 378 men and women by examining whether occupational physical activity affects longevity. The large number of cases; long duration of follow-up; linkage to detailed registry data on socioeconomic factors updated during follow-up; and adjustment for smoking by detailed data on smoking status, leisure-time physical activity, and measured anthropometric data allow more robust modelling of the associations between occupational physical activity and longevity.

Implications of all the available evidence

Our results contrast with a so-called physical activity paradox and suggest a positive dose–response relationship between occupational physical activity and longevity in men. This finding might have public health implications suggesting that all activity is beneficial, regardless of domain, and might inform future public health recommendations on physical activity. However, additional research is needed investigating why occupational physical activity appears to be differently associated with longevity between men and women.

To overcome some of the shortcomings of previous studies, we aimed to estimate the effect of occupational physical activity on longevity using data from a nationally representative sample comprising more than 430 000 Norwegian individuals. Among these individuals, occupational physical activity was assessed by the same instrument and with information on socioeconomic factors, such as education and income, LTPA, and other potentially confounding variables.

Methods Study design and participantsWe used data from the Norwegian population-based health examination surveys done between February, 1974, and November, 2002, by the National Health Screening Service (later the Norwegian Institute of Public Health). The surveys covered all parts of Norway and were done with a similar methodological framework,Bjartveit K Foss OP Gjervig T Lund-Larsen PG The cardiovascular disease study in Norwegian counties. Background and organization.Bjartveit K Stensvold I Lund-Larsen PG Gjervig T Kruger O Urdal P Cardiovascular screenings in Norwegian counties. Background and implementation. Status of risk pattern during the period 1986-90 among persons aged 40–42 years in 14 counties.Naess O Søgaard AJ Arnesen E et al.Cohort profile: cohort of Norway (CONOR). which facilitated harmonisation and pooling of data. Data from the health examination surveys were linked to the National Population and Housing Censuses and the Norwegian Cause of Death Registry by use of the participants' unique personal identification number. Permission to be absolved from professional secrecy and linking of the data was granted by the Regional Ethics Committee South-East (2009/605/REK [updated Feb 7, 2019]). The study complies with the Declaration of Helsinki.We used surveys from The Norwegian Counties Study,Bjartveit K Foss OP Gjervig T Lund-Larsen PG The cardiovascular disease study in Norwegian counties. Background and organization. with an overall participation rate of 87·7%; the Age 40 programme,Bjartveit K Stensvold I Lund-Larsen PG Gjervig T Kruger O Urdal P Cardiovascular screenings in Norwegian counties. Background and implementation. Status of risk pattern during the period 1986-90 among persons aged 40–42 years in 14 counties. with a rate of 73·5%; and the CONOR study,Naess O Søgaard AJ Arnesen E et al.Cohort profile: cohort of Norway (CONOR). with a rate 58·3% (figure 1). Participants were excluded if they were aged younger than 18 years or older than 65 years at study entry, had missing data on occupational physical activity or confounding variables, participated more than once within or between surveys, or died within 1 month of study entry. For participants with multiple participations within or between surveys, the earliest participation with valid data on occupational physical activity was used.Figure thumbnail gr1

Figure 1Study profile

*In The Norwegian Counties Study, the exact number of individuals invited is unknown; therefore, 921 962 and 219 045 refer to the number of invitations, not individuals invited. 94 034 individuals participated at least once in The Norwegian Counties Study, of which 88 008 met the inclusion criteria for this study. †661 775 and 192 135 refer to the number of participations, not the number of individuals who participated. ‡Due to risk minimisation in data protection, exact age in days at study entry was not available but calculated by subtracting year and month of birth from year and month at study entry (clinical examination). The 11 participants who died within the same month that they entered the study could, therefore, not be included in survival modelling.

 Exposure assessmentOccupational physical activity was assessed at study entry by the Saltin-Grimby Physical Activity Level Scale with four mutually exclusive options (appendix p 1).Physiological analysis of middle-aged and old former athletes. Comparison with still active athletes of the same ages. Briefly, participants indicated their level of occupational physical activity during the past year from the following: mostly sedentary work (eg, desk work or work including assembling of minor parts), work characterised by some walking (eg, light industrial work, non-sedentary office work, inspection, etc), work characterised by walking and lifting (eg, mail delivery and construction work), or work characterised by heavy manual labour (eg, digging and shovelling). All participants responding to the occupational physical activity question were considered to be part of the workforce, including full-time homemakers. For brevity throughout this Article, the four categories are referred to as sedentary, walking, walking and lifting, and heavy labour. Covariates

Data on education level, income, and ethnicity were obtained from the National Population and Housing Censuses done in 1970, 1980, 1990, and 2001. Highest attained education level between study entry and the last census was categorised into one of five levels corresponding to the current Norwegian standard: (1) basic (≤10 years of education); (2) intermediate 1 (11–12 years of education); (3) intermediate 2 (13–14 years of education); (4) higher education or undergraduate (14–17 years of education); and (5) higher education, graduate, or postgraduate (≥18 years of education). Personal income was categorised into census-specific quintiles (men and women separately), with the highest recorded quintile during follow-up used in statistical modelling. Ethnic background was categorised into Nordic (ie, individuals from Norway, Sweden, Denmark, Finland, Iceland, or Faroe Islands) and non-Nordic (ie, first-generation immigrants without a Nordic background or individuals born in a Nordic country to non-Nordic parents).

Height was measured to the nearest 0·1 cm and weight to the nearest 0·1 kg by trained research nurses, and body-mass index (BMI) was calculated with the standard formula (kg/m2). Data on smoking status (ie, never, former, or current), number of cigarettes smoked daily (ie, currently or in the past), and years of smoking were categorised into smoking grade: (1) never smoked; (2) former smoker with less than 20 pack-years; (3) former smoker with 20 pack-years or more; (4) current daily smoker with less than 20 pack-years; and (5) current daily smoker with 20 pack-years or more.

Self-reported data on history of myocardial infarction, stroke, diabetes, angina pectoris, and use of antihypertensive medications were categorised into prevalent cardiovascular disease categories: no prevalent cardiovascular disease; angina pectoris or hypertension; or myocardial infarction, stroke, or diabetes.

Non-fasting blood samples were collected and analysed for serum cholesterol and triglycerides. In the earlier surveys (1974–85), blood pressure was measured twice with sphygmomanometers and the second recording was selected. From 1985 onwards, three automatic oscillometric measurements (Dinamap; Criticon, Tampa, FL, USA) were taken and the average of the last two available measurements were selected. In individuals with automatic blood pressure assessment, resting heart rate was measured sitting down and used as a proxy for cardiorespiratory fitness in sensitivity analyses.

LTPA was assessed by the Saltin-Grimby Physical Activity Level Scale in most participants (348 383 [80%]). Participants indicated their usual level of LTPA during the past year by choosing from the response categories: reading, watching television, or engaging in sedentary activities (ie, sedentary); walking, bicycling, or engaging in other types of physical activity at least 4 h a week (ie, light LTPA); exercising to keep fit and participating in recreational athletics at least 4 h a week (ie, moderate LTPA); or regular, vigorous training or participating in competitive sports several times a week (ie, high LTPA). For the remaining 20% of participants (88 995), LTPA was assessed by the instrument used in the CONOR study.Graff-Iversen S Anderssen SA Holme IM Jenum AK Raastad T Two short questionnaires on leisure-time physical activity compared with serum lipids, anthropometric measurements and aerobic power in a suburban population from Oslo, Norway. For the purpose of this study, LTPA for these remaining participants was harmonised into the Saltin-Grimby Physical Activity Level Scale (appendix p 1). Outcome assessmentParticipants were followed up prospectively from study entry (between February, 1974, and November, 2002) until death or end of follow-up on Dec 31, 2018, whichever came first. Data were all-cause mortality, mortality from cardiovascular disease (International Classification of Diseases [ICD]-8 codes 390–444·1, 444·3–458, 782·4; ICD-9 codes 390–459; ICD-10 codes I00–I99), and mortality from cancer (ICD-8 codes 140–209; ICD-9 codes 140–208; ICD-10 codes C00–C97), which were obtained during follow-up from the Norwegian Cause of Death Registry.Data quality in the Causes of Death Registry. Statistical analysis

The significance of differences in background characteristics between participants in the four categories of occupational physical activity was assessed by pairwise comparisons, following simple linear (ie, continuous variables) and logistic (ie, categorical variables) regression analysis.

All associations of occupational physical activity with all-cause and cause-specific mortality were estimated with flexible parametric survival models (stpm2 package for Stata [version 15.0]).Further development of flexible parametric models for survival analysis. Age (months) was used as the timescale and we adjusted all models for birth cohort (1920–29, 1930–39, 1940–49, 1950–59, 1960–69, ≥1970). Because the proportional hazards assumption was violated for several models and because shortcomings of the hazard ratio (HR) are being increasingly recognised,Stensrud MJ Røysland K Ryalen PC On null hypotheses in survival analysis. we analysed associations between occupational physical activity and mortality using differences in restricted mean survival time (RMST) with 95% CIs as effect sizes.Uno H Claggett B Tian L et al.Moving beyond the hazard ratio in quantifying the between-group difference in survival analysis. Time-varying HRs are presented in the appendix (pp 8–10). Because several studies have indicated different associations between occupational physical activity and mortality in men and women,Coenen P Huysmans MA Holtermann A et al.Do highly physically active workers die early? A systematic review with meta-analysis of data from 193 696 participants. we stratified all analyses by sex.On the basis of a priori directed acyclic graphs (appendix p 5), analyses were done with several levels of adjustment. Model A (crude model) was adjusted for age (timescale), sex (stratification), and so-called calendar effects (10-year birth cohorts); model B used model A and adjusted for highest attained education and income level by 2002, ethnicity, prevalent cardiovascular disease, and smoking; and model C used model B and adjusted for BMI and LTPA. Both models B and C can be regarded as finally adjusted, depending on whether or not LTPA and BMI are viewed as mediators (ie, model B) or as part of the confounding structure (ie, model C). Total cholesterol, triglycerides, and blood pressure were considered to be mediators (appendix p 5); therefore, these data are presented as background characteristics but are not included in the multivariable-adjusted model. Because BMI and LTPA might be considered as part of the confounding structure for mortality associated with occupational physical activity or as intermediates,Nooijen CFJ Del Pozo-Cruz B Nyberg G Sanders T Galanti MR Forsell Y Are changes in occupational physical activity level compensated by changes in exercise behavior?.Ekelund U Kolle E Steene-Johannessen J et al.Objectively measured sedentary time and physical activity and associations with body weight gain: does body weight determine a decline in moderate and vigorous intensity physical activity?. we present unadjusted and adjusted results as forest plots, but summarise results from model C in the text. Sensitivity analysesFirst, because cardiorespiratory fitness can be considered a confounder (a prerequisite of occupational physical activity and associated with mortality riskKodama S Saito K Tanaka S et al.Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis.), we reanalysed model C with adjustment for resting heart rate as a marker of cardiorespiratory fitness in 412 054 participants (appendix pp 6–7). Second, we investigated potential bias from reverse causation (ie, that diagnosed or undiagnosed subclinical disease leads to changes in occupational physical activity) by restricting model C to participants without known cardiovascular disease (eg, angina pectoris, hypertension, myocardial infarction, stroke, or diabetes) at study entry who survived the first 5 years of follow-up (n=415 549; appendix pp 6–7). Third, younger (aged 50 years) were assumed more likely to change their level of occupational physical activity during follow-up (eg, by completing their education or retiring soon after study entry); therefore, we also restricted the supplementary model 2 (appendix pp 6–7) to include only the 372 832 participants (85·2%) aged 30–50 years at study entry. Role of the funding source

The funders of the Norwegian population-based health examination surveys had no role in study design, data collection, data analysis, data interpretation, or writing of the report.

ResultsWe included 213 079 men and 224 299 women, with a median age of 41·3 years (IQR 40·3–42·6) at health survey examination (table). 59 565 (13·6%) individuals entered the study between 1974 and 1979, 114 754 (26·2%) during the 1980s, 239 609 (54·8%) during the 1990s, and 23 450 (5·4%) between 2000 and 2002, with approximately equal proportions of men and women across study entry decades. Additional background characteristics by occupational physical activity category and sex can be found in the appendix (p 3).

TableBaseline characteristics of study participants by sex

Data are mean (SD) or n (%). For p values with each variable and activity category, see the appendix (p 2).

During a median of 28 years (IQR 25–31) from study entry to the end of follow-up on Dec 31, 2018, 74 203 (17·0%) of the participants died (all-cause mortality); 20 111 (27·1%) of the deaths were due to cardiovascular disease and 29 886 (40·3%) were due to cancer. About two-thirds of all deaths were caused by cardiovascular disease or cancer across occupational physical activity categories in both sexes; however, the proportion of men and women dying from the two causes varied, as did the proportion of people across occupational physical categories.

In men, crude analysis (model A) suggested that higher occupational physical activity was associated with lower life expectancy, especially for mortality from cardiovascular disease. However, the results did not indicate a clear dose–response relationship, with the walking and lifting category having the shortest life expectancy (figure 2A). Results were reversed in models B and C and suggested a positive dose–response relationship; higher occupational physical activity was associated with higher life expectancy. In model C, men in the walking, walking and lifting, and heavy labour categories had life expectancies equivalent to 0·4 (95% CI −0·1 to 1·0), 0·8 (0·3 to 1·3), and 1·7 (1·2 to 2·3) years longer, respectively, than men in the sedentary referent category (figure 2C). Corresponding differences were smaller for cardiovascular disease-specific mortality (0·5 years [0·2 to 0·7]) and cancer-specific mortality (0·7 years [0·3 to 1·1]) when comparing the heavy labour category with the sedentary referent; however, the dose–response patterns were similar to those for all-cause mortality (figure 2C). Although slight attenuations and accentuations of associations from model C were observed in the sensitivity analyses (supplementary models 1–3; appendix pp 6–7), the overall patterns were not materially different.Figure thumbnail gr2

Figure 2Prospective associations between occupational physical activity and mortality from all causes, cardiovascular disease, and cancer in men

(A) Model A was adjusted for age (timescale), sex (stratification), and so-called calendar effects (10-year birth cohorts). (B) Model B used model A and adjusted for highest education level attained between study entry and Dec 31, 2001 (five levels), ethnicity (either Nordic or first-generation immigrant without Nordic background or an individual born in a Nordic country [ie, Norway, Sweden, Denmark, Finland, Iceland, or Faroe Islands] to non-Nordic parents), prevalent cardiovascular disease (no prevalent disease; angina pectoris or hypertension; myocardial infarction, stroke, or diabetes), smoking ([1] never; [2] former and <20 pack-years; [3] former and ≥20 pack-years; [4] current daily and <20 pack-years; and [5] current daily and ≥20 pack-years), and income (highest attained sample quintile by 2002). (C) Model C used model B and adjusted for body-mass index (continuous) and leisure-time physical activity (four levels).

In women, results from neither crude nor multivariable-adjusted models indicated any clear beneficial or detrimental association between occupational physical activity and mortality (figure 3). In model C, the only estimate with a 95% CI not including unity was found in the walking and lifting group when cardiovascular disease mortality was modelled as the outcome, indicating a shorter life expectancy compared with the sedentary reference group (figure 3C). However, this finding was not robust in sensitivity analyses (appendix p 7).Figure thumbnail gr3

Figure 3Prospective associations between occupational physical activity and mortality from all causes, cardiovascular disease, and cancer in women

(A) Model A was adjusted for age (timescale), sex (stratification), and so-called calendar effects (10-year birth cohorts). (B) Model B used model A and adjusted for highest education level attained between study entry and Dec 31, 2001 (five levels), ethnicity (either Nordic or first-generation immigrant without Nordic background or an individual born in a Nordic country [ie, Norway, Sweden, Denmark, Finland, Iceland, or Faroe Islands] to non-Nordic parents), prevalent cardiovascular disease (no prevalent disease; angina pectoris or hypertension; myocardial infarction, stroke, or diabetes), smoking ([1] never; [2] former and <20 pack-years; [3] former and ≥20 pack-years; [4] current daily and <20 pack-years; and [5] current daily and ≥20 pack-years), and income (highest attained sample quintile by 2002). (C) Model C used model B and adjusted for body-mass index (continuous) and leisure-time physical activity (four levels).

Discussion

Men in occupations characterised by high physical activity had shorter life expectancies than did men in mainly sedentary occupations. However, after multivariable adjustment including comprehensive information on markers of socioeconomic status and other confounding factors, we found no evidence that high occupational physical activity per se leads to a shorter life expectancy. Instead, our results suggest there might be a positive dose–response relationship between occupational physical activity and longevity in men. This finding was supported in analyses of cause-specific mortality and in sensitivity analyses exploring robustness to reverse causation. By contrast, neither crude nor multivariable-adjusted results indicated an association between occupational physical activity and mortality in women.

In men, our results contrast with a recently indicated so-called physical activity paradox, suggesting detrimental effects of high occupational physical activity on mortality.Coenen P Huysmans MA Holtermann A et al.Do highly physically active workers die early? A systematic review with meta-analysis of data from 193 696 participants.Holtermann A Krause N van der Beek AJ Straker L The physical activity paradox: six reasons why occupational physical activity (OPA) does not confer the cardiovascular health benefits that leisure time physical activity does. When confounding variables were taken into account, our results indicate that occupational physical activity, like overall physical activity and LTPA, might increase longevity.Ekelund U Dalene KE Tarp J Lee IM Physical activity and mortality: what is the dose response and how big is the effect?. Therefore, we suggest residual confounding from the complex network of socioeconomic and behavioural factors associated with occupational physical activity as a more plausible explanation for the previously observed higher mortality rate with physical activity during work in men. A meta-analysis examining the association between occupational physical activity and mortality suggested an 18% higher risk of all-cause mortality with high occupational physical activity than with low activity. However, five of the included studies suggested lower mortality, five suggested higher mortality, and six observed no association with higher occupational physical activity.Coenen P Huysmans MA Holtermann A et al.Do highly physically active workers die early? A systematic review with meta-analysis of data from 193 696 participants. Studies published after this meta-analysis have been equally inconsistent, and an umbrella review prepared for the 2020 WHO Physical Activity Guideline Development Group suggested inverse associations between occupational physical activity and incidence of some cancers, coronary heart disease, and type 2 diabetes, all of which are major contributors to premature mortality.Cillekens B Lang M van Mechelen W et al.How does occupational physical activity influence health? An umbrella review of 23 health outcomes across 158 observational studies. Nevertheless, individuals with high occupational physical activity had higher risk of all-cause mortality than did those with low activity. Additionally, several important limitations of studies investigating the association between occupational physical activity and mortality have been highlighted.Is there a ‘recent occupational paradox’ where highly active physically active workers die early? Or are there failures in some study methods?. Our results add further nuances, extend previous work, and suggest that there is little evidence to support a detrimental effect of occupational physical activity on longevity in men.Although corroborating previous observations,Coenen P Huysmans MA Holtermann A et al.Do highly physically active workers die early? A systematic review with meta-analysis of data from 193 696 participants. we can only speculate about the observed differences between men and women in associations between occupational physical activity and longevity. Although less likely, one possible explanation is that doing the same amount of (occupational) physical activity might yield different effects on longevity in men and women.Hands B Parker H Larkin D Cantell M Rose E Male and female differences in health benefits derived from physical activity: implications for exercise prescription. However, it is also possible that men and women perceive the intensity of occupational physical activity differently, and that men and women self-selected into the same occupational physical activity categories were exposed to different physiological effort.Coenen P Huysmans MA Holtermann A et al.Do highly physically active workers die early? A systematic review with meta-analysis of data from 193 696 participants. Factors associated with occupational physical activity, such as

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