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Long working hours may increase risk for stroke, CHD
Employees who worked more than 55 hours in a week had a significant increased risk for incident CHD and stroke, according to results of a recent systematic review and meta-analysis.
Researchers analyzed 25 published and unpublished prospective studies of 24 cohorts in the United States, Europe and Australia. They performed a meta-analysis to assess CHD risk among 603,838 participants (mean follow-up, 8.5 years; 5.1 million person-years) and a separate analysis to assess stroke risk among 528,908 participants (mean follow-up, 7.2 years; 3.8 million person-years). All participants were free of CHD or stroke at baseline in the respective analyses.
Overall, 4,768 CHD events and 1,722 stroke events occurred during follow-up. After adjustment for age, sex and socioeconomic status, employees who worked 55 hours or more per week had a significantly increased risk for incident CHD (RR = 1.13; 95% CI, 1.02-1.26) and stroke (RR = 1.33; 95% CI, 1.11-1.61) compared with employees who worked 35 to 40 hours per week, which the researchers classified as a standard work week.
The researchers also observed a dose-response relationship between working hours and stroke. The greatest increase was among those who worked 55 hours or more per week (RR = 1.33; 95% CI, 1.11-1.61), followed by 49 to 54 hours (RR = 1.27; 95% CI, 1.03-1.56) and 41 to 48 hours (RR = 1.1; 95% CI, 0.94-1.28), when compared with a 35- to 40-hour work week.
No significant evidence of bias was observed as a result of confounding, reverse causation, study quality or other factors, according to the researchers.
Restricting analysis to high-quality studies indicated that socioeconomic status influenced the link between CHD and working hours, with a greater risk increase with lower socioeconomic status (RR = 2.18; 95% CI, 1.25-3.81 for the lowest group vs. RR = 0.87; 95% CI, 0.55-1.38 for the highest group).
The association between long working hours and CV risk was not influenced by sex or geographical region.
“Our meta-analysis shows that employees who work long hours have a higher risk of stroke than those working standard hours,” the researchers concluded. “However, the evidence for CHD is less persuasive. Our findings suggest that more attention should be paid to the management of vascular risk factors in individuals who work long hours.”
According to Urban Janlert, MD, PhD, from the department of public health and clinical medicine at Umeå University, Umeå, Sweden, this study is “pioneering” due to its large scale and inclusion of stroke as an endpoint. The results represent the strongest indication thus far of a link between CVD and stroke, Janlert wrote in an accompanying editorial.
“Long working hours are not a negligible occurrence,” Janlert wrote. “That the length of a working day is an important determinant mainly for stroke, but perhaps also for CHD, is an important finding. ... Essentially, if long working hours present a danger to health, it should be possible to change them, which is not always the case with other work environmental factors.” – by Adam Taliercio
Disclosure: The researchers and Janlert report no relevant financial disclosures.