Working 55+ hours a week raises stroke risk by a third, pooled data show

People who work 55 hours or more a week have about a 33% higher risk of stroke than those working a standard 35–40 hours, according to a meta-analysis of more than half a million people, with a smaller 13% increase in coronary heart disease [s2]. Scaled to the world's workforce, the World Health Organization and International Labour Organization estimate that exposure to long working hours was linked to 745,194 deaths from heart disease and stroke in 2016 [s1] — a large public-health total built from a modest per-person risk.

The individual-level evidence

The per-person numbers come from a 2015 Lancet study that pooled published and unpublished cohort data on 603,838 people for coronary heart disease and 528,908 for stroke, all free of the relevant disease at baseline [s2]. Over follow-up it recorded 4,768 coronary events and 1,722 strokes [s2]. Compared with standard hours, working 55 hours or more a week was associated with a relative risk of 1.13 (95% CI 1.02–1.26) for incident coronary heart disease and 1.33 (1.11–1.61) for stroke [s2].

Two features make the stroke finding the more persuasive of the two. It showed a dose-response gradient — relative risks of 1.10 for 41–48 hours, 1.27 for 49–54 hours, and 1.33 for 55 or more, with a significant trend [s2] — and it held up when the authors tested for reverse causation and adjusted for other risk factors, with estimates staying in the range of 1.30 to 1.42 [s2]. The heart-disease association was weaker and less robust [s2]. The authors' own interpretation was cautious: the practical implication is closer monitoring of vascular risk factors in people who work long hours, not a claim that hours alone drive the disease [s2].

Scaling to a global burden

The WHO/ILO Joint Estimates took that risk evidence and applied it to the world's working population [s1]. In 2016, an estimated 488 million people — 8.9% of the global population — were exposed to long working hours of 55 or more per week [s1]. Applying the relative risks to WHO's disease-burden data yielded 745,194 attributable deaths and 23.3 million disability-adjusted life-years lost from heart disease and stroke combined [s1]. Long hours accounted for an estimated 3.7% of the global ischaemic-heart-disease burden and 6.9% of the stroke burden, measured as deaths [s1].

Two caveats sit inside those totals. The estimate assumes the relative risks from mostly high-income cohorts transfer to the whole world, and it is a modelled attribution — deaths are inferred by applying population-attributable fractions to total disease burdens, not counted case by case [s1]. The authors are explicit that this is the largest such attributable burden of any occupational risk factor they have estimated, which is a statement about how many people are exposed as much as about how dangerous the exposure is per person [s1].

Why hours might damage the vascular system

The proposed pathways are behavioural and physiological. Long hours are linked to a chronic stress response, higher blood pressure, less sleep, and less time for physical activity and healthy eating — all established cardiovascular risks. The stroke-specific gradient is consistent with a stress-and-blood-pressure mechanism, though the pooled studies could not isolate which pathway carries the effect [s2]. Related occupational exposures point the same way: unpredictable work schedules are associated with worse sleep, one of the plausible intermediate steps between long or erratic hours and vascular disease.

What the evidence does not show

None of this is medical advice, and the individual increase is modest — a relative risk of 1.33 for stroke means the exposure raises an individual's baseline risk by roughly a third, not that long hours make a stroke likely [s2]. Both bodies of evidence are observational, so residual confounding by the kind of person who works very long hours cannot be excluded [s1][s2]. The economic reading is that long hours are a health cost of how work is organised and paid — most concentrated where low hourly wages force long weeks — and that the burden is large precisely because the exposure is so common [s1].

What to watch

The WHO/ILO estimates stop at 2016, and the question is what the shift toward remote and hybrid work has done to the share of people logging 55-plus-hour weeks. The metric to track is exposure prevalence: if the fraction working extreme hours falls, the attributable burden falls with it, independent of any change in the per-person risk. Updated Joint Estimates, and national working-time surveys, are where that trend will show up.

Sources

• [s1] Global, regional, and national burdens of ischemic heart disease and stroke attributable to exposure to long working hours for 194 countries, 2000–2016 — Environment International (WHO/ILO Joint Estimates), published September 2021. https://doi.org/10.1016/j.envint.2021.106595
• [s2] 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 — The Lancet, published 31 October 2015. https://doi.org/10.1016/S0140-6736(15)60295-1