TitleLong working hours and risk of coronary heart disease and stroke: a systematic review and meta-analysis of published and unpublished data for 603,838 individuals.
Publication TypeJournal Article
Year of Publication2015
AuthorsKivimäki, M, Jokela, M, Nyberg, ST, Singh-Manoux, A, Fransson, EI, Alfredsson, L, Bjorner, JB, Borritz, M, Burr, H, Casini, A, Clays, E, De Bacquer, D, Dragano, N, Erbel, R, Geuskens, GA, Hamer, M, Hooftman, WE, Houtman, IL, Jöckel, K-H, Kittel, F, Knutsson, A, Koskenvuo, M, Lunau, T, Madsen, IEH, Nielsen, ML, Nordin, M, Oksanen, T, Pejtersen, JH, Pentti, J, Rugulies, R, Salo, P, Shipley, MJ, Siegrist, J, Steptoe, A, Suominen, SB, Theorell, T, Vahtera, J, Westerholm, PJM, Westerlund, H, O'Reilly, D, Kumari, M, Batty, GD, Ferrie, JE, Virtanen, M
Corporate AuthorsIPD-Work Consortium
JournalLancet
Volume386
Issue10005
Pagination1739-46
Date Published10/2015
ISSN1474-547X
KeywordsAge Factors, Coronary Disease, Female, Humans, Male, Middle Aged, Risk, Risk Factors, Sex Factors, Socioeconomic Factors, Stroke, Work Schedule Tolerance
Abstract
 

BACKGROUND: Long working hours might increase the risk of cardiovascular disease, but prospective evidence is scarce, imprecise, and mostly limited to coronary heart disease. We aimed to assess long working hours as a risk factor for incident coronary heart disease and stroke.

METHODS: We identified published studies through a systematic review of PubMed and Embase from inception to Aug 20, 2014. We obtained unpublished data for 20 cohort studies from the Individual-Participant-Data Meta-analysis in Working Populations (IPD-Work) Consortium and open-access data archives. We used cumulative random-effects meta-analysis to combine effect estimates from published and unpublished data.

FINDINGS: We included 25 studies from 24 cohorts in Europe, the USA, and Australia. The meta-analysis of coronary heart disease comprised data for 603,838 men and women who were free from coronary heart disease at baseline; the meta-analysis of stroke comprised data for 528,908 men and women who were free from stroke at baseline. Follow-up for coronary heart disease was 5·1 million person-years (mean 8·5 years), in which 4768 events were recorded, and for stroke was 3·8 million person-years (mean 7·2 years), in which 1722 events were recorded. In cumulative meta-analysis adjusted for age, sex, and socioeconomic status, compared with standard hours (35-40 h per week), working long hours (≥55 h per week) was associated with an increase in risk of incident coronary heart disease (relative risk [RR] 1·13, 95% CI 1·02-1·26; p=0·02) and incident stroke (1·33, 1·11-1·61; p=0·002). The excess risk of stroke remained unchanged in analyses that addressed reverse causation, multivariable adjustments for other risk factors, and different methods of stroke ascertainment (range of RR estimates 1·30-1·42). We recorded a dose-response association for stroke, with RR estimates of 1·10 (95% CI 0·94-1·28; p=0·24) for 41-48 working hours, 1·27 (1·03-1·56; p=0·03) for 49-54 working hours, and 1·33 (1·11-1·61; p=0·002) for 55 working hours or more per week compared with standard working hours (ptrend<0·0001).

INTERPRETATION: Employees who work long hours have a higher risk of stroke than those working standard hours; the association with coronary heart disease is weaker. These findings suggest that more attention should be paid to the management of vascular risk factors in individuals who work long hours.

FUNDING: Medical Research Council, Economic and Social Research Council, European Union New and Emerging Risks in Occupational Safety and Health research programme, Finnish Work Environment Fund, Swedish Research Council for Working Life and Social Research, German Social Accident Insurance, Danish National Research Centre for the Working Environment, Academy of Finland, Ministry of Social Affairs and Employment (Netherlands), US National Institutes of Health, British Heart Foundation.

DOI10.1016/S0140-6736(15)60295-1
Alternate JournalLancet
PubMed ID26298822
Grant List / / British Heart Foundation / United Kingdom
RG/13/2/30098 / / British Heart Foundation / United Kingdom
G0100222 / / Medical Research Council / United Kingdom
K013351 / / Medical Research Council / United Kingdom
MR/K013351/1 / / Medical Research Council / United Kingdom
R01AG034454 / AG / NIA NIH HHS / United States
R01HL036310 / HL / NHLBI NIH HHS / United States