Anusha Boyanpally, MD
Long working hours (LWH) may be a risk factor for cardiovascular diseases and stroke (1). There is limited evidence on the association of LWH and increased risk of stroke (2, 3). Fadel et al. have reported association of LWH and risk of stroke in a large French population-based cohort.
The study included randomly selected adults aged 18 to 69 years from the CONSTANCES cohort. Data was obtained from self-administered questionnaires, health examinations, and physician diagnosed stroke cases at affiliated health-screening centers. The authors have categorized working years of exposures as >1 year, 1 – <10 years, and ≥10 years. Variables included are; age, sex, smoking, occupation, history of stroke, age occurrence of stroke, diabetes, high blood pressure, dyslipidemia (both hypercholesteremia or hypertriglyceridemia), family history of cardiovascular events and body mass index. The study has excluded patients with part-time jobs, and history of stroke.
In the final sample of 143592, 1124 (0.9%) had stroke, 42542 (29.6%) reported LWH and 14481 (10.1%) had LWH for more than 10 years. LWH for ≥ 10 years were associated with higher risk of stroke (adjusted odds ratio, 1.45; [95% CI, 1.21-1.74]). Younger population had a higher risk of stroke in those with LWH for ≥ 10 years (adjusted odds ratio, 2.28; [95% CI, 1.46-3.58]). Similarly, high-skilled white-collar jobs and low skilled white-collar jobs had more risk of stroke than professional jobs and blue-collar jobs.
This study has several limitations. The study did not take into account whether the working hours were sedentary or involved physical exertion, as sedentary lifestyle is associated with diabetes mellitus, hypertension and hyperlipidemia, which exacerbate the risk of stroke. The authors have not considered history of atrial fibrillation, myocardial infarction, chronic kidney disease, (4) and history of cancer (5), which are associated with stroke. Race differences were not included in the study, which has a significant association with stroke (6). Also, the severity of the risk factors (uncontrolled versus controlled hypertension, oral hypoglycemics versus insulin dependent diabetes) was not assessed. Authors have included subjects with missing data and considered as not having stroke instead of excluding from the study. Level of exercise, number of sleep hours, and food habits are other significant factors that determine the stroke risk, which were not investigated in this study. As the study was limited to the French population, results may vary with different countries having different working conditions and government-imposed policies. Strokes were not studied in detail whether they were ischemic versus hemorrhagic strokes, and not sub-analyzed into large vessel, small vessel or cardioembolic strokes. The higher odds of stroke in a younger population may be explained by job stress and other psychological factors (7) which are not measured in the study.
Despite above limitations, this is a comprehensive study which included all types of strokes and adjusted for modifiable risk factors. Improved job exposure matrices are needed to quantify the level of work exposure and assess the association with stroke. Further studies are required to be conducted in a structured working environment to evaluate stroke incidence in this population.
1. Van der Hulst M. Long workhours and health. Scand J Work Environ Health. 2003;29:171–188.
2. Kivimäki M et al; IPD-Work Consortium. Long working hours and risk of coronary heart disease and stroke: a systematic review and meta-analysis of published and unpublished data for 603,838 individuals. Lancet. 2015;386:1739–1746. doi: 10.1016/S0140-6736(15)60295-1
3. Hannerz H et al; Long working hours and stroke among employees in the general workforce of Denmark. Scand J Public Health. 2018;46:368–374. doi: 10.1177/1403494817748264
4. Bakhtawar K. Mahmoodi et al; Association of Kidney Disease Measures With Ischemic Versus Hemorrhagic Strokes Pooled Analyses of 4 Prospective Community-Based Cohorts. Originally published1 Jul 2014, Stroke. 2014;45:1925–1931
5. Dearborn JL et al; Stroke and Cancer- A Complicated Relationship. J Neurol Transl Neurosci. 2014;2(1):1039.
6. Racial differences in recurrent ischemic stroke risk and recurrent stroke case fatality. Karen C. Albright et al; Neurology Nov 2018, 91 (19) e1741-e1750; DOI:10.1212/WNL.0000000000006467
7. Kotlega D et al; The emotional stress and risk of ischemic stroke. Neurol Neurochir Pol. 2016 Jul-Aug;50(4):265-70. doi: 10.1016/j.pjnns.2016.03.006. Epub 2016 Mar 23.