Cumulative Exposure to Long Working Hours and Occurrence of Ischemic Heart Disease: Evidence From the CONSTANCES Cohort at Inception

Relationship between long working hours and smoking behaviors: Evidence from population-based cohort studies in Korea

OBJECTIVES

Long working hours and overwork are growing public health concerns in the Western-Pacific region. We explored the relationship between working hours and smoking behaviors of Korean workers.

METHODS

This study included 284 782 observations (50 508 workers) from four nationwide cohort studies in Korea. Using generalized estimating equations, we estimated the associations of working hours with current smoking status, smoking initiation, and smoking cessation within each cohort. Cohort-specific estimates were combined through random-effect meta-analysis. Effect sizes were presented as odds ratios (OR) and 95 confidence intervals (CI).

RESULTS

The overall smoking prevalence was 26.8% within the cohorts. The adjusted OR (95% CI) of the association between working hours and current smoking were 1.01 (0.94-1.08) for <35 hours/week, 1.04 (1.01-1.09) for 41-48 hours/week, 1.06 (1.01-1.10) for 49-54 hours/week, and 1.07 (1.04-1.10) for ≥55 hours/week compared with 35-40 hours/week. The adjusted OR (95% CI) of the association between working hours and smoking cessation in the follow-up were 0.93 (0.85-1.02) for <35 hours/week, 0.89 (0.83-0.96) for 41-48 hours/week, 0.87 (0.81-0.95) for 48-54 hours/week, and 0.91 (0.85-0.98) for ≥55 hours/week compared with 35-40 hours/week. No clear associations were observed between working hours and smoking initiation.

CONCLUSION

Long working hours are associated with high current smoking risk and reduced likelihood of smoking cessation among Korean workers. Policy interventions are required to promote smoking cessation and reduce excess overwork for individuals experiencing long working hours.

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.

Association between weekly working hours and risky alcohol use: A 12-year longitudinal, nationwide study from South Korea

We aimed to investigate the association between long working hours and onset of risky alcohol use. We included a nationally representative sample comprising 11,226 workers in South Korea (57,887 observations). The Alcohol Use Disorders Identification Test was used to assess risky alcohol use. Fixed effect regressions were employed to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Adjusted ORs (95% CIs) of risky alcohol use were 1.08 (0.95-1.22) for 41-48 h/week, 1.12 (0.96-1.31) for 49-54 h/week, and 1.40 (1.21-1.63) for ≥55 h/week, compared with standard working hours (35-40 h/week). ORs (95% CIs) of the association between working ≥55 h/week and risky alcohol use was 1.39 (1.17-1.65) for men and 1.34 (0.98-1.82) for women. Yearly cumulative exposure to long working hours (>40 h/week) is positively associated with risky alcohol use in a dose-dependent manner. For instance, exposure to long working hours for ≥3 years was associated with an increased likelihood of risky alcohol use (OR [95% CI]: 2.20 [1.78-2.72]). Sex-stratified analyses showed that long work hours are associated with risky alcohol use in both male and female workers. Appropriate work-hour policy is needed to prevent workers from risky alcohol use.

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.

Long working hours, sedentary work, noise, night shifts and risk of ischaemic heart disease

OBJECTIVE

Ischaemic heart disease (IHD) is a leading cause of death in Western countries. The aim of this study was to examine the associations between occupational exposure to loud noise, long working hours, shift work, and sedentary work and IHD.

METHODS

This data linkage study included all New Zealanders employed and aged 20-64 years at the time of the 2013 census, followed up for incident IHD between 2013 and 2018 based on hospitalisation, prescription and death records. Occupation and number of working hours were obtained from the census, and exposure to sedentary work, loud noise and night shift work was assessed using New Zealand job exposure matrices. HRs were calculated for males and females using Cox regression adjusted for age, socioeconomic status, smoking and ethnicity.

RESULTS

From the 8 11 470 males and 7 83 207 females employed at the time of the census, 15 012 male (1.9%) and 5595 female IHD cases (0.7%) were identified. For males, there was a modestly higher risk of IHD for the highest category (>90 dBA) of noise exposure (HR 1.19; 95% CI 1.07 to 1.33), while for females exposure prevalence was too low to calculate an HR. Night shift work was associated with IHD for males (HR 1.10; 95% CI 1.05 to 1.14) and females (HR 1.25; 95% CI 1.17 to 1.34). The population attributable fractions for night shift work were 1.8% and 4.6%, respectively. No clear associations with working long hours and sedentary work were observed.

CONCLUSIONS

This study suggests that occupational exposures to high levels of noise and night shift work might be associated with IHD risk.

Gender dimension in cardio-pulmonary continuum

Cardio-pulmonary diseases, which were once regarded as a man's illness, have been one of the leading causes of morbidity and mortality for both men and women in many countries in recent years. Both gender and sex influence the functional and structural changes in the human body and therefore play an important role in disease clinical manifestation, treatment choice, and/or response to treatment and prognosis of health outcomes. The gender dimension integrates sex and gender analysis in health sciences and medical research, however, it is still relatively overlooked suggesting the need for empowerment in the medical research community. Latest advances in the field of cardiovascular research have provided supportive evidence that the application of biological variables of sex has led to the understanding that heart disease in females may have different pathophysiology compared to males, particularly in younger adults. It has also resulted in new diagnostic techniques and a better understanding of symptomatology, while gender analysis has informed more appropriate risk stratification and prevention strategies. The existing knowledge in the pulmonary field shows the higher prevalence of pulmonary disorders among females, however, the role of gender as a socio-cultural construct has yet to be explored for the implementation of targeted interventions. The purpose of this review is to introduce the concept of gender dimension and its importance for the cardiopulmonary continuum with a focus on shared pathophysiology and disease presentation in addition to interrelation with chronic kidney disease. The review presents basic knowledge of what gender dimension means, and the application of sex and gender aspects in cardiovascular medicine with a specific focus on early pulmonary development, pulmonary hypertension, and chronic obstructive pulmonary disease (COPD). Early vascular aging and inflammation have been presented as a potential pathophysiological link, with further interactions between the cardiopulmonary continuum and chronic kidney disease. Finally, implications for potential future research have been provided to increase the impact of gender dimension on research excellence that would add value to everybody, foster toward precision medicine and ultimately improve human health.

Global, regional, and national burdens of ischemic heart disease and stroke attributable to exposure to long working hours for 194 countries, 2000-2016: A systematic analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury

BACKGROUND

World Health Organization (WHO) and International Labour Organization (ILO) systematic reviews reported sufficient evidence for higher risks of ischemic heart disease and stroke amongst people working long hours (≥55 hours/week), compared with people working standard hours (35-40 hours/week). This article presents WHO/ILO Joint Estimates of global, regional, and national exposure to long working hours, for 194 countries, and the attributable burdens of ischemic heart disease and stroke, for 183 countries, by sex and age, for 2000, 2010, and 2016.

METHODS AND FINDINGS

We calculated population-attributable fractions from estimates of the population exposed to long working hours and relative risks of exposure on the diseases from the systematic reviews. The exposed population was modelled using data from 2324 cross-sectional surveys and 1742 quarterly survey datasets. Attributable disease burdens were estimated by applying the population-attributable fractions to WHO's Global Health Estimates of total disease burdens.

RESULTS

In 2016, 488 million people (95% uncertainty range: 472-503 million), or 8.9% (8.6-9.1) of the global population, were exposed to working long hours (≥55 hours/week). An estimated 745,194 deaths (705,786-784,601) and 23.3 million disability-adjusted life years (22.2-24.4) from ischemic heart disease and stroke combined were attributable to this exposure. The population-attributable fractions for deaths were 3.7% (3.4-4.0) for ischemic heart disease and 6.9% for stroke (6.4-7.5); for disability-adjusted life years they were 5.3% (4.9-5.6) for ischemic heart disease and 9.3% (8.7-9.9) for stroke.

CONCLUSIONS

WHO and ILO estimate exposure to long working hours (≥55 hours/week) is common and causes large attributable burdens of ischemic heart disease and stroke. Protecting and promoting occupational and workers' safety and health requires interventions to reduce hazardous long working hours.

Cumulative Exposure to Long Working Hours and Occurrence of Ischemic Heart Disease: Evidence From the CONSTANCES Cohort at Inception

Background

Long‐working hours (LWH) are a probable risk factor for ischemic heart diseases (IHD); however, no previous study has considered duration of exposure to LWH when addressing this topic. We aimed to determine the association between cumulative exposure to LWH and IHD while accounting for relevant confounders.

Methods and Results

In this retrospective study, we included all baseline participants from the French population‐based cohort CONSTANCES. Part‐time employees and those who reported a cardiac event in the 5 years before LWH exposure were excluded. From self‐administered questionnaires and clinical examinations, we obtained participants’ age, sex, body mass index, occupational status, smoking habits, high blood pressure, diabetes mellitus, familial history of cardiovascular disease, dyslipidemia, exposure to LWH, and its duration. We defined LWH as working for >10 hours daily for at least 50 days per year. The main outcome was reported history of IHD, ie, myocardial infarction or angina pectoris, during a clinical examination. Of 137 854 included participants, 69 774 were men. There were 1875 cases (1.36%) of IHD, and exposure to LWH was reported by 42 462 subjects (30.8%) among whom 14 474 (10.50%) reported exposure for at least 10 years. Overall, exposure to LWH for ≥10 years was associated with an increased risk of IHD, adjusted odds ratio (aOR) 1.24 (1.08–1.43), P=0.0021. In stratified analyses, this effect was not observed in women, but was significant amongst men, aOR 1.28 (1.11–1.48), P=0.0008.

Conclusions

This large population‐based study supports an association between cumulative exposure to LWH and IHD in men. Future research should consider relevant strategies for reducing LWH exposure and duration.