TY - JOUR

T1 - Long working hours and risk of coronary heart disease and stroke

T2 - a systematic review and meta-analysis of published and unpublished data for 603,838 individuals

AU - Kivimäki, Mika

AU - Jokela, Markus

AU - Nyberg, Solja T

AU - Singh-Manoux, Archana

AU - Fransson, Eleonor I

AU - Alfredsson, Lars

AU - Bjorner, Jakob B

AU - Borritz, Marianne

AU - Burr, Hermann

AU - Casini, Annalisa

AU - Clays, Els

AU - De Bacquer, Dirk

AU - Dragano, Nico

AU - Erbel, Raimund

AU - Geuskens, Goedele A

AU - Hamer, Mark

AU - Hooftman, Wendela E

AU - Houtman, Irene L

AU - Jöckel, Karl-Heinz

AU - Kittel, France

AU - Knutsson, Anders

AU - Koskenvuo, Markku

AU - Lunau, Thorsten

AU - Madsen, Ida E H

AU - Nielsen, Martin L.

AU - Nordin, Maria

AU - Oksanen, Tuula

AU - Pejtersen, Jan H

AU - Pentti, Jaana

AU - Rugulies, Reiner

AU - Salo, Paula

AU - Shipley, Martin J

AU - Siegrist, Johannes

AU - Steptoe, Andrew

AU - Suominen, Sakari B

AU - Theorell, Töres

AU - Vahtera, Jussi

AU - Westerholm, Peter J M

AU - Westerlund, Hugo

AU - O'Reilly, Dermot

AU - Kumari, Meena

AU - Batty, G David

AU - Ferrie, Jane E

AU - Virtanen, Marianna

AU - IPD-Work Consortium

N1 - Copyright © 2015 Kivimäki et al. Open Access article distributed under the terms of CC BY. Published by Elsevier Ltd.. All rights reserved.

PY - 2015/10/31

Y1 - 2015/10/31

N2 - 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 We obtained unpublished data for 20 cohort studies from the Individual-Participant-Data Meta-analysis in Working Populations (IPD-Work) Consortium and open-access data archives. We used cumulative random-effects meta-analysis to combine effect estimates from published and unpublished data.FINDINGS: We included 25 studies from 24 cohorts in Europe, the USA, and Australia.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.

AB - 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.

KW - Age Factors

KW - Coronary Disease

KW - Female

KW - Humans

KW - Male

KW - Middle Aged

KW - Risk

KW - Risk Factors

KW - Sex Factors

KW - Socioeconomic Factors

KW - Stroke

KW - Work Schedule Tolerance

U2 - 10.1016/S0140-6736(15)60295-1

DO - 10.1016/S0140-6736(15)60295-1

M3 - Review

C2 - 26298822

VL - 386

SP - 1739

EP - 1746

JO - The Lancet

JF - The Lancet

SN - 0140-6736

IS - 10005

ER -