Long working hours and change in body weight: analysis of individual-participant data from 19 cohort studies

Association between long working hours and metabolic dysfunction-associated steatotic liver disease: a nationwide population-based study in Korea

OBJECTIVES

Long working hour is a known risk factor for metabolic diseases. We explored the association between working hours and metabolic dysfunction-associated steatotic liver disease (MASLD).

STUDY DESIGN

Data on working hours among 22,818 workers (11,999 females) from the Korea National Health and Nutrition Examination Survey (2013-2021) were used for this study.

METHODS

MASLD was defined as a combination of hepatic steatosis combined with one or more of cardiometabolic risk factors (overweight/obesity, prediabetes/diabetes, raised blood pressure, hypertriglyceridemia, low high-density lipoprotein cholesterol). Hepatic steatosis was assessed using the hepatic steatosis index. Logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

The overall prevalence of MASLD was 30.4% in men and 18.1% in women. Among male workers, 20.2% worked ≥55 h/week, whereas among female workers, 10.1% worked ≥55 h/week. Compared with working 35-40 h/week, working ≥55 h/week was positively associated with overweight/obesity (OR: 1.21; 95% CI: 1.05-1.40), pre-diabetes mellitus (pre-DM)/DM (OR: 1.20; 95% CI: 1.04-1.38), raised blood pressure (OR: 1.17; 95% CI: 1.02-1.35), and presence of any cardiometabolic risk factors (OR: 1.56; 95% CI: 1.21-2.02). The adjusted OR (95% CI) of the association between working hours and MASLD was 1.27 (1.09-1.47) for ≥55 h/week compared with working 35-40 h/week in male workers. In female workers, long working hours were not clearly associated with cardiometabolic risk factors and MASLD.

CONCLUSION

Long working hours are positively associated with MASLD among Korean male workers. Policy interventions are needed to mitigate the adverse metabolic effects of prolonged working hours.

Rotating shift and BMI increase among healthcare workers in a military hospital: pre- and post-pandemic analysis in Taiwan

Background

The increasing prevalence of high body mass index (BMI) emphasizes the need for action. Understanding of BMI factors among military hospital healthcare workers remains limited. This study aims to address this gap by analyzing BMI risk factors and changes pre- and post-coronavirus 2019 pandemic among military hospital healthcare workers in central Taiwan from 2019 to 2021.

Methods

Conducted at a military hospital in central Taiwan, this study analyzed anonymized health examination data from 2019 to 2021 for 483 healthcare workers. We performed generalized estimating equations to investigate trends in BMI and its association with various factors, including age, sex, job titles, military status, job tenure, work shifts, and lifestyle habits.

Results

The risk of increased BMI was higher in 2021 compared to 2019 (risk ratio [RR]: 1.008, 95% confidence interval [CI]: 1.001-1.014). Individuals on rotating shifts had a higher risk of increased BMI compared to day shift workers (RR: 1.021; 95% CI: 1.008-1.035) and higher odds of obesity (odds ratio: 1.546; 95% CI: 1.099-2.175). Among obese individuals, BMI in soldiers was approximately 4.9% lower than in non-soldiers (RR: 0.951; 95% CI: 0.915-0.988).

Conclusions

This study identified a significant post-pandemic increase in BMI among healthcare workers in a Taiwanese military hospital, with rotating shifts being a key risk factor for both increased BMI and obesity. Work-related factors influenced BMI changes among obese individuals, while non-work-related factors were significant for non-obese individuals. These findings highlight the broader effects of the pandemic and the specific impact of work-related factors on obese healthcare workers.

Association between long working hours and diet quality and patterns: A latent profile analysis of a nationally representative sample of Korean workers

BACKGROUND

Long working hours are associated with cardiovascular and metabolic diseases. This study investigated the relationship between the working hours and dietary qualities and patterns in Korean workers.

METHODS

Data from 24,523 workers were extracted from the Korea National Health and Nutrition Examination Survey, 2013-2021. The Korean Healthy Eating Index (KHEI), which ranges from 0 to 100, with a higher score indicating greater adherence to Korean dietary guidelines and superior dietary quality, was used for dietary assessment. We identified dietary patterns and classified workers using latent profile analysis. Logistic regressions were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Five distinct dietary patterns emerged: healthy diet (24.8%), low-vegetable diet (14.0%), average diet (7.8%), low-fruit diet (31.4%), and poor diet (22.0%). The mean KHEI score was 60.8, with the highest score observed in the healthy diet pattern (71.3) and the lowest, in the poor diet pattern (50.0). Compared with working 35-40 h/week, working ≥55 h/week was negatively associated with KHEI scores (β: -1.08; 95% CI: -1.67, -0.49). Those working ≥55 h/week were less likely to have a healthy diet pattern (OR: 0.81; 95% CI: 0.72, 0.91) and more likely to have a low-fruit diet (OR: 1.36; 95% CI: 1.20, 1.55) or poor diet pattern (OR: 1.23; 95% CI: 1.05, 1.43) compared with those working 35-40 h/week.

CONCLUSION

Long working hours are associated with undesirable dietary quality and patterns. Policy interventions aimed at enhancing dietary quality are needed to alleviate the health burdens associated with long working hours.

Employment Factors Associated With Long Working Hours in France

The objectives of the study were to explore the employment factors associated with long working hours, known as a risk factor for various health outcomes. The study relied on the national representative data of the 2013 French working conditions survey and a study sample of 23,378 full-time employees. Long working hours were defined by the threshold of 48 hours a week following the European Working Time Directive. The prevalence of long working hours was higher among men (13.5%) than among women (8.5%). Employees of the private sector, with permanent work contract, in small companies, and men in the services had a higher prevalence of exposure. This prevalence increased with educational and occupational levels. Our findings may help decision-makers to define preventive strategies. More research is needed to improve our knowledge of the employment factors associated with long working hours, as there may be strong differences between countries.

Causal effect of obesity on the probability of employment in women in Turkey

This study aims to investigate the causal effect of obesity on the employment probability of women in Turkey via the instrumental variable approach by using data from the 2018 Turkey and Demographic Health Survey. Obesity prevalence in the area of living and the overweight status of the oldest child, which are the most common types of instruments seen in the literature, are used as instruments. Consistent with the OLS result, the 2SLS estimate indicates that obese women are statistically significantly less likely to be employed when the overweight status of the child is used as an instrument. On the other hand, the statistically significant effect of obesity disappears when the area level obesity prevalence is used as the instrument. In addition, obesity in women decreases the likelihood of employment in the services sector and full-time jobs and employment with social security. Although the results of this study do not indicate the source of the effect found, the presence of a causal relationship for women should not be ignored when the economic burden of obesity for Turkey is considered.

Association between long working hours and cigarette smoking, leisure-time physical activity, and risky alcohol use: Findings from the Korea National Health and Nutrition Examination Survey (2014-2021)

BACKGROUND

Long working hours cause adverse health outcomes; however, the precise mechanisms underlying this relationship remain unknown. We examined the association between long working hours and health behaviors, as well as gender differences in this association.

METHODS

A nationally representative sample of 26,385 Korean workers was analyzed. The exposure variable was self-reported weekly working hours. The outcomes examined were cigarette smoking, high-level physical activity (defined as engaging in ≥150 min/week of moderate-to-vigorous leisure-time physical activity), and risky alcohol use (defined as consuming seven glasses for men or five glasses for women of alcohol in a single sitting, twice or more per week). Logistic regression models were utilized, and gender differences were examined by incorporating interaction terms into the regression models.

RESULTS

Among 26,385 workers, 4,109 (16%) worked ≥55 h/week. The prevalence of cigarette smoking, high-level physical activity, and risky alcohol use was 19%, 18%, and 14%, respectively. The odds ratio (OR) (95% confidence interval [CI]) of the association between working ≥55 h/week and outcomes was 1.26 (1.12-1.43) for cigarette smoking, 0.73 (0.65-0.83) for high-level physical activity, and 0.95 (0.83-1.08) for risky alcohol use compared to working 35-40 h/week. A moderating effect of gender on the association between long working hours and risky alcohol use was observed. The OR (95% CI) of the association between working ≥55 h/week was 0.88 (0.76-1.02) in men and 1.51 (1.12-2.05) in women.

CONCLUSION

Our findings emphasize the need for policy interventions aimed at reducing excessive working hours and fostering healthy lifestyle behaviors among individuals engaged in long working hours.

Working hours and the onset of suicidal ideation and depressive symptoms: A 10-year nationwide longitudinal study in South Korea (2012-2022)

Long working hours are associated with adverse health outcomes. We investigated the association between working hours and suicidal ideation and depressive symptoms. We analyzed a nationally representative sample of 11,116 Korean workers, comprising 64,661 observations from 2012 to 2022, to investigate how working hours were associated with mental health problems. To account for repeated measurements in each participant, we employed a generalized estimating equation to estimate risk ratios (RRs) and 95% confidence intervals (CIs). Of the total observations, 13.1% reported working ≥55 h/week. The RR (95% CI) of the association between long working hours and onset of suicidal ideation in the subsequent year was 1.20 (0.95-1.53) for 41-48 h, 1.35 (1.02-1.78) for 49-54 h, and 1.56 (1.23-1.98) for ≥55 h/week, compared to 35-40 h/week. The RR (95% CI) of the association between long working hours and onset of depressive symptoms in the subsequent year was 1.19 (1.07-1.34) for 41-48 h, 1.11 (0.97-1.28) for 49-54 h, and 1.24 (1.10-1.40) for ≥55 h per week, compared to 35-40 h/week. Those working fewer than 35 h/week also had an increased risk of suicidal ideation and depressive symptoms. Policy interventions are needed to reduce excess working hours and protect workers' mental health.

Association between long working hours and physical inactivity in middle-aged and older adults: a Korean longitudinal study (2006-2020)

BACKGROUND

We investigated associations for long working hours in relation to physical inactivity and high-level physical activity among middle-aged and older adults.

METHODS

Our study included 5402 participants and 21 595 observations from the Korean Longitudinal Study of Ageing (2006-2020). Logistic mixed models were used to estimate ORs and 95% CIs. Physical inactivity was defined as not engaging in any type of physical activity, while high-level physical activity was defined as engaging in ≥150 min per week of physical activity.

RESULTS

Working >40 hours weekly was positively related to physical inactivity (OR (95% CI) 1.48 (1.35 to 1.61)) and negatively related to high-level physical activity (0.72 (95% CI 0.65 to 0.79)). Exposure to long working hours consecutively for ≥3 waves was associated with the highest OR for physical inactivity (1.62 (95% CI 1.42 to 1.85)) and the lowest OR for high-level physical activity (0.71 (95% CI 0.62 to 0.82)). Furthermore, compared with persistent short working hours (≤40 hours → ≤40 hours), long working hours in a previous wave (>40 hours → ≤40 hours) were associated with a higher OR of physical inactivity (1.28 (95% CI 1.11 to 1.49)). Exposure to an increase in working hours (≤40 hours → >40 hours) was also associated with a higher OR of physical inactivity (1.53 (95% CI 1.29 to 1.82)).

CONCLUSION

We found that having working long hours was associated with a higher risk of physical inactivity and a lower likelihood of high-level physical activity. Moreover, accumulation of long working hours was associated with a higher risk of physical inactivity.

Association between prolonged exposure to long working hours and stroke subtypes in the CONSTANCES cohort

BACKGROUND

Though there is increasing evidence on the effect of long working hours (LWH) and stroke, few studies have distinguished stroke subtypes. We examined the associations between LWH and ischaemic or haemorrhagic stroke after adjusting for cardiovascular risk factors.

METHODS

From a national population-based cohort CONSTANCES, baseline questionnaires and initial health examinations were used to retrieve sociodemographic and cardiovascular risk factors from 2012 to 2018. LWH were defined as self-reported working time≥10 hours daily for at least 50 days per year. Incident cases of stroke were collected using International Classification of Disease codes recorded in the National Health Data System. Associations between LWH and stroke were investigated using multinomial models adjusted for cardiovascular risk factors.

RESULTS

Among the 160 751 participants who were free from stroke at baseline, exposure to LWH≥10 years was reported by 20 723 participants, and 190 incident cases of stroke were identified, including 134 ischaemic and 56 haemorrhagic. Exposure to LWH was associated with an elevated odds of ischaemic stroke (OR=1.61 (1.04-2.49)) and haemorrhagic stroke (OR=2.50 (1.38-4.53)) in unadjusted models. In adjusted multivariable models, only the LWH association with haemorrhagic stroke remained significant (aOR=1.92 (1.01-3.09)).

CONCLUSIONS

LWH were associated with stroke, though it remained significant for haemorrhagic stroke only after adjustments. Differences in direct and indirect biological pathways and lack of power in the ischaemic subgroup may explain these results and further studies on the impact of mediating and effect measure modifying factors are needed. Nevertheless, policies that attenuate effects of both LWH and cardiovascular risks factor are warranted.

Impact of Reduced Working Hours and Night Work Hours on Metabolic Syndrome: A Quasi-Experimental Study

Objectives

Epidemiological evidence linking long working hours and shift work to metabolic syndrome remains inadequate. We sought to evaluate the impact of reducing working hours on metabolic syndrome.

Methods

We compared the prevalence of metabolic syndrome among male manual workers in a manufacturing company (N = 371) before and after the introduction of policy to reduce daily work hours from 10 to 8 hours. Components of metabolic syndrome were measured in periodic health examinations before the intervention, 6-9 months after, and 1.5-2 years after the intervention. Generalized estimating equation models were used to estimate changes in the prevalence of metabolic syndrome. Analyses were stratified by day work versus shift work.

Results

The results showed a significantly decreased prevalence of metabolic syndrome 6-9 months following the intervention in day workers (risk ratio = 0.68, 95% confidence interval 0.52-0.88), but the benefit disappeared after 1.5-2 years. Shift workers showed a decreased prevalence of metabolic syndrome for the whole follow-up duration after the intervention, although the change was not statistically significant.

Conclusion

Reducing working hours was associated with short-term improvement in metabolic syndrome in male manual workers.

The association between long working hours and obstructive sleep apnea assessed by STOP-BANG score: a cross-sectional study

PURPOSE

The relationship between night-shift work and obstructive sleep apnea (OSA) is well known, but that between OSA and long working hours is still unknown. This study explores the association between long working hours and OSA.

METHODS

Using cross-sectional Korean National Health and Nutrition Examination Survey 2020 data, we made multiple logistic regression models to calculate odds ratios (ORs) between weekly working hours and STOP-BANG scores for OSA screening. Stratified regression models by night or rotating shift work were also made.

RESULTS

In an adjusted model of STOP-BANG high-risk versus low-risk groups, the OR in the group exceeding 40 h/wk was higher but not statistically significant, 1.19 [95% confidence interval (CI) 0.66-2.15] compared to the group working 40 h/wk (standard working hours) or less. In the group exceeding 52 h/wk, the OR was 2.03 with statistical significance (95% CI 1.08-3.80). In the stratification analysis of daytime and night-shift work, the daytime worker results were similar to those in the non-stratified model. The point estimation values of ORs in the night-shift workers were higher than in the daytime workers; however, we did not observe a statistical significance.

CONCLUSION

Long working hours can increase the risk of OSA assessed by STOP-BANG scores.

Association between precarious employment and BMI in the United States

OBJECTIVE

There is growing recognition that precarious employment is an important determinant of health, which may increase BMI through multiple mechanisms, including stress. It was investigated whether increases in precarious employment were associated with changes in BMI in the United States.

METHODS

Data were from the National Longitudinal Survey of Youth adult cohort (1996-2016) (N = 7280). Thirteen indicators were identified to operationalize seven dimensions of precarious employment (range: 0-7, 7 indicating most precarious): material rewards, working-time arrangements, stability, workers' rights, collective organization, interpersonal relationships, and training. The precarious employment-BMI association was estimated using linear regression models and an instrumental variables approach; state- and individual-level firm sizes were the instruments for precarious employment. Models also included individual and year fixed effects and controlled for age, marital status, education, region, and industry.

RESULTS

The average precarious employment score (PES) was 3.49 (95% CI: 3.46-3.52). The PES was the highest among Hispanic (4.04; 95% CI: 3.92-4.15) and non-Hispanic Black (4.02; 95% CI: 3.92-4.12) women with lower education. A 1-point increase in the PES was associated with a 2.18-point increase in BMI (95% CI: 0.30-4.01).

CONCLUSIONS

Given that even small changes in weight affect chronic disease risk, policies to improve employment quality warrant consideration.

The multiple roles of life stress in metabolic disorders

The activation of stress-related neuroendocrine systems helps to maintain homeostasis, but excessive stress can damage body functions. We review current evidence from basic sciences and epidemiology linking stress to the development and progression of metabolic disorders throughout life. Findings from rodents demonstrate that stress can affect features of metabolic dysfunction, such as insulin resistance, glucose and lipid homeostasis, as well as ageing processes such as cellular senescence and telomere length shortening. In human studies, stressors in the home, workplace and neighbourhood are associated with accelerated ageing and metabolic and immune alterations, both directly and indirectly via behavioural risks. The likelihood of developing clinical conditions, such as diabetes mellitus and hepatic steatosis is increased in individuals with adverse childhood experiences or long-term (years) or severe stress at work or in private life. The increased risk of metabolic disorders is often associated with other stress-related conditions, such as mental health disorders, cardiovascular disease and increased susceptibility to infections. Equally, stress can worsen prognosis in metabolic diseases. As favourable modifications in stressors are associated with reductions in incidence of metabolic disorders, further investigation of the therapeutic value of targeting stress in personalized medicine is warranted.

Working Hours, Sleep Disturbance and Self-Assessed Health in Men and Women: A Multilevel Analysis of 30 Countries in Europe

Objectives

This study examined the gender and cross-country differences in the relationship between working hours and self-assessed health among working men and women in Europe, and further explored the moderating role of sleep disturbance in the relationship.

Methods

We used cross-sectional data from the 6th European Working Condition Survey on 14,603 men and 15,486 women across 30 countries in Europe. A multivariate logistic regression was applied to evaluate the relationship between working hours, sleep disturbance, and self- assessed health. In addition, we employed a two-stage multilevel logistic regression to assess the cross-country variations in the relationship between working hours and self-assessed health.

Results

The study showed a slightly U-shaped relationship between working hours and less-than-good self-assessed health among working adults in Europe (<31 h: aOR = 1.11; 95% CI: 1.00-1.25, 41-50 h: aOR = 0.98; 95% CI: 0.84-1.15, and 50+ h: aOR = 1.31; 95% CI: 1.07-1.59). However, working men had higher odds of reporting less-than-good self-assessed health as compared to women when they devote longer hours to paid work. The results further showed that there are cross-country variations in the association between working hours and less-than-good self-assessed health for both men and women, and that men had slightly lower variations as compared to women. Contrary to expectation, sleep disturbance did not moderate the relationship between working hours and less-than-good self-assessed health for both men and women in Europe.

Conclusions

Although there are gender differences and cross-country variations in the association between working hours and less-than-good self-assessed health, sleep disturbance did not moderate the associations. These findings underscore the importance for strict work time regulation and generous work-family policies that may promote good working conditions and health.

Trajectories of working hours in later careers and their association with social and health-related factors: a follow-up study

BACKGROUND

The aim was to identify working hours' trajectories in later work careers over a follow-up of 15-17 years and to examine their association with social factors and health.

METHODS

A subsample from the Helsinki Health Study was extracted comprising employees of the City of Helsinki, Finland. Growth mixture modelling was used to identify different working hour trajectories. Age, gender, occupational class, marital status, health behaviour, physical and mental functioning and current pain were associated with trajectory membership. Relative risks (RRs) and their 95% confidence intervals (CIs) were estimated.

RESULTS

A two-trajectory model was selected: 'Stable regular working hours' (90%) and 'Shorter and varying working hours' (10%). Women (RR 1.40, 95% CI 1.09-1.78), the oldest employees (RR 2.71, 95% CI 2.06-3.57), managers and professionals (RR 1.56, 95% CI 1.20-2.02), those reporting non-drinker (RR 1.66, 95% CI 1.32-2.10), those reporting sleeping more than 8 h per night (RR 1.74 95% CI 1.25-2.42) and those reporting poor mental functioning (RR 1.39 95% CI 1.15-1.68) had higher likelihood of belonging to the trajectory 'Shorter and varying working hours'. There were no differences between the trajectories in marital status, smoking, body mass index, current pain or physical functioning. However, routine non-manual workers (RR 0.74, 95% CI 0.55-0.98), and semi-professionals (RR 0.70, 95% CI 0.50-0.96) had lower likelihood of belonging to this trajectory.

CONCLUSIONS

Trajectories of working hours in later work career differ by age, gender and occupational class but also by health behaviours and mental health functioning.

Coping Strategies Influence Cardiometabolic Risk Factors in Chronic Psychological Stress: A Post Hoc Analysis of A Randomized Pilot Study

Chronic psychological stress can result in physiological and mental health risks via the activation of the hypothalamic–pituitary–adrenal (HPA) axis, sympathoadrenal activity and emotion-focused coping strategies. The impact of different stress loads on cardiometabolic risk is poorly understood. This post hoc analysis of a randomized pilot study was conducted on 61 participants (18–65 years of age) with perceived chronic stress. The Perceived Stress Questionnaire (PSQ₃₀), Psychological Neurological Questionnaire (PNF), anthropometric, clinical and blood parameters were assessed. Subjects were assigned to ‘high stress’ (HS; PSQ₃₀ score: 0.573 ± 0.057) and ‘very high stress’ (VHS; PSQ₃₀ score: 0.771 ± 0.069) groups based on the PSQ₃₀. Morning salivary cortisol and CRP were elevated in both groups. Visceral adiposity, elevated blood pressure and metabolic syndrome were significantly more frequent in the HS group vs. the VHS group. The fatty liver index (FLI) was higher (p = 0.045), while the PNF score was lower (p < 0.001) in the HS group. The HS group was comprised of more smokers (p = 0.016). Energy intake and physical activity levels were similar in both groups. Thus, high chronic stress was related to visceral adiposity, FLI, elevated blood pressure and metabolic syndrome in the HS group, while very high chronic stress was associated with psychological–neurological symptoms and a lower cardiometabolic risk in the VHS group, probably due to different coping strategies.

Multilevel Analysis of Urban-Rural Variations of Body Weights and Individual-Level Factors among Women of Childbearing Age in Nigeria and South Africa: A Cross-Sectional Survey

Background: An unhealthy body weight is an adverse effect of malnutrition associated with morbidity among women of childbearing age. While there is increasing attention being paid to the body weights of children and adolescents in Nigeria and South Africa, a major surge of unhealthy body weight in women has received less attention in both countries despite its predominance. The purpose of this study was to explore the prevalence of body weights (underweight, normal, overweight, and obese) and individual-level factors among women of childbearing age by urban-rural variations in Nigeria and South Africa. Methods: This study used the 2018 Nigeria Demographic Health Survey data (n = 41,821) and 2016 South Africa Demographic Health Survey (n = 8514). Bivariate, multilevel, and intracluster correlation coefficient analyses were used to determine individual-level factors associated with body weights across urban-rural variations. Results: The prevalence of being overweight or obese among women was 28.2% and 44.9%, respectively, in South Africa and 20.2% and 11.4% in Nigeria. A majority, 6.8%, of underweight women were rural residents in Nigeria compared to 0.8% in South Africa. The odds of being underweight were higher among women in Nigeria who were unemployed, with regional differences and according to breastfeeding status, while higher odds of being underweight were found among women from poorer households, with differences between provinces and according to cigarette smoking status in South Africa. On the other hand, significant odds of being overweight or obese among women in both Nigeria and South Africa were associated with increasing age, higher education, higher wealth index, weight above average, and traditional/modern contraceptive use. Unhealthy body weights were higher among women in clustering areas in Nigeria who were underweight (intracluster correlation coefficient (ICC = 0.0127), overweight (ICC = 0.0289), and obese (ICC = 0.1040). Similarly, women of childbearing age in clustering areas in South Africa had a lower risk of experiencing underweight (ICC = 0.0102), overweight (ICC = 0.0127), and obesity (ICC = 0.0819). Conclusions: These findings offer a deeper understanding of the close connection between body weights variations and individual factors. Addressing unhealthy body weights among women of childbearing age in Nigeria and South Africa is important in preventing disease burdens associated with body weights in promoting Sustainable Development Goal 3. Strategies for developing preventive sensitization interventions are imperative to extend the perspectives of the clustering effect of body weights on a country level when establishing social and behavioral modifications for body weight concerns in both countries.

Length of exposure to long working hours and night work and risk of sickness absence: a register-based cohort study

Background

There is inconsistent evidence that long working hours and night work are risk factors for sickness absence, but few studies have considered variation in the length of exposure time window as a potential source of mixed findings. We examined whether the association of long working hours and night work with sickness absence is dependent on the length of exposure to the working hour characteristics.

Methods

We analysed records of working hours, night work and sickness absence for a cohort of 9226 employees in one hospital district in Finland between 2008 and 2019. The exposure time windows ranged from 10 to 180 days, and we used Cox’s proportional hazards models with time-dependent exposures to analyse the associations between working-hour characteristics and subsequent sickness absence.

Results

Longer working hours for a period of 10 to 30 days was not associated with the risk of sickness absence whereas longer working hours for a period of 40 to 180 days was associated with a lower risk of sickness absence. Irrespective of exposure time window, night work was not associated with sickness absence.

Conclusions

It is important to consider the length of exposure time window when examining associations between long working hours and sickness absence, whereas the association between night work and sickness absence is not similarly sensitive to exposure times.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-021-07231-4.

A longitudinal study of working hours and chronic kidney disease in healthy workers: The Kangbuk Samsung Health Study

OBJECTIVES

Long working hours are linked to an increased risk of exposure to work safety hazards that threaten the health of workers. To date, only a few cross-sectional studies regarding the relationship between working characteristics, such as over-workload and chronic kidney disease (CKD) have been reported. Therefore, in this longitudinal study, we aimed to examine the direct relationship between long working hours and the incidence of CKD.

METHODS

We included 97 856 participants without CKD in the Kangbuk Samsung Health Study. Using a self-report questionnaire, we evaluated weekly working hours, which were categorized into 35-40, 41-52, and >52 hours. CKD was defined as estimated glomerular filtration rate <60 mL/min/1.73 m2 . Hazard ratios (HRs) and 95% confidence intervals (CIs) for incident CKD were estimated using Cox proportional hazards regression analyses with weekly working 35-40 hours as the reference.

RESULTS

During a median follow-up of 4.0 years, 185 participants developed incident CKD (incidence density, 4.83 per 104 person-years). Multivariable-adjusted HRs (95% CI) of incident CKD for weekly working >52 hours compared with working 35-40 hours were 1.99 (1.22-3.25). In subgroup analyses, the significant association between working >52 hours and incident CKD was consistently observed in groups of age ≥40 years, men, and obesity with no interaction.

CONCLUSIONS

Our large-scale cohort study of young- to middle-aged men and women demonstrated a significant association between long working hours and an increased risk of incident CKD.

Timing of Entry into Paid Employment, Adverse Physical Work Exposures and Health: The Young Helsinki Health Study

It is not well known how the timing of entry into paid employment and physical work exposures contribute to different health outcomes in young employees. Thus, we determined the associations of age at entry into paid employment and physical work exposures with general and mental health in young employees and determined whether associations differ by behavior-related risk factors. Data were collected via online and mailed surveys in autumn 2017 from employees of the City of Helsinki aged 18–39 years (n = 5897; 4630 women and 1267 men, response rate 51.5%). Surveys comprised measures of age at entry into paid employment, seven working conditions, behavior-related risk factors and health outcomes (self-rated health [SRH] and common mental disorders [CMD] as generic indicators of physical and mental health). Logistic regression analysis was used. After full adjustment, age at entry was not associated with the health outcomes; however, in additional analyses, younger age at first employment was associated with smoking and obesity (OR 3.00, 95% CI 2.34–3.85 and 1.67, 95% CI 1.32–2.11 for those started working at age of ≤18 years, respectively). Of the working conditions, sitting and standing were positively associated with poor SRH and CMD and uncomfortable working postures with CMD. Working conditions were broadly similarly associated with health outcomes among those with and without behavior-related risk factors. Although we found little support for modification by behavior-related risk factors, overweight, obesity and smoking were associated with poor SRH and binge drinking and smoking with CMD. Additionally, moderate and high levels of leisure-time physical activity were inversely associated with poor SRH. In conclusion, early entry into paid employment appears not to associate to immediate poorer health in young employees, although it was associated with smoking and obesity even after full adjustment. Exposure to physically heavy work and uncomfortable working postures may increase the risk of adverse health outcomes.

Work participation and physicality of work in young adulthood and the development of unhealthy lifestyle habits and obesity later in life: a prospective cohort study

OBJECTIVE

To determine the effects of early entry into the labour market and physicality of work in young adulthood on the development of obesity and unhealthy lifestyle habits later in life.

METHODS

This study is a part of the Young Finns Study. Entry into the labour market and physicality of work were measured at baseline, when participants were aged 18, 21, or 24 years in 1986 or 18 years in 1989. Follow-up of lifestyle habits were conducted in 2001, 2007 and 2011. The outcomes were obesity (n=5558 observations), abdominal obesity (n=4060 observations), daily smoking (n=5628) and leisure time physical activity (n=5946) and analysed with generalised estimating equation.

RESULTS

Compared with sedentary work, physicality of work in young adulthood increased the odds of future obesity (adjusted OR=1.32, 95% CI 1.01 to 1.74 for light/moderate work and OR=1.44, 95% CI 0.99 to 2.08 for heavy manual work (particularly in women OR=2.03, 95% CI 1.07 to 3.84)) and future smoking (OR=1.79, 95% CI 1.39 to 2.30 for light/moderate work and OR=2.01, 95% CI 1.47 to 2.76 for heavy manual work (particularly in women OR=2.81, 95% CI 1.60 to 4.91)). For those who entered the labour market at ages 18-21 or younger, the odds of smoking was 1.85 times (95% CI 1.26 to 2.73) and that of obesity 1.45 times (95% CI 1.01 to 2.10) higher, and the rate of leisure time physical activity was 0.73 times (95% CI 0.58 to 0.93) lower compared with those who entered the labour market at ages 22-24 years.

CONCLUSION

Early entry into the labour market and physicality of work in young adulthood shape the development of obesity and unhealthy behaviours in later adulthood.