title: 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working hours and risk of coronary heart disease and stroke: a systematic review and meta-analysis of published and unpublished data for 603,838 individuals.
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 We obtained unpublished data for 20 cohort studies from the Individual-Participant-Data Meta-analysis in Working Populations (IPD-Work) Consortium and open-access data archives. We used cumulative random-effects meta-analysis to combine effect estimates from published and unpublished data.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
  
  
  BACKGROUND
  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.
authors: Department of Epidemiology and Public Health, University College London, London, UK; Faculty of Medicine, University of Helsinki, Helsinki, Finland. Electronic address: m.kivimaki@ucl.ac.uk.
authors: Mika
authors: M
authors: Kivimäki
authors: Institute of Behavioral Sciences, University of Helsinki, Helsinki, Finland.
authors: Markus
authors: M
authors: Jokela
authors: Finnish Institute of Occupational Health, Helsinki, Tampere and Turku, Finland.
authors: Solja T
authors: ST
authors: Nyberg
authors: Department of Epidemiology and Public Health, University College London, London, UK; Inserm U1018, Centre for Research in Epidemiology and Population Health, Villejuif, France.
authors: Archana
authors: A
authors: Singh-Manoux
authors: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; School of Health Sciences, Jönköping University, Jönköping, Sweden; Stress Research Institute, Stockholm University, Stockholm, Sweden.
authors: Eleonor I
authors: EI
authors: Fransson
authors: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; Centre for Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden.
authors: Lars
authors: L
authors: Alfredsson
authors: National Research Centre for the Working Environment, Copenhagen, Denmark.
authors: Jakob B
authors: JB
authors: Bjorner
authors: Department of Occupational Medicine, Koege Hospital, Copenhagen, Denmark.
authors: Marianne
authors: M
authors: Borritz
authors: Federal Institute for Occupational Safety and Health (BAuA), Berlin, Germany.
authors: Hermann
authors: H
authors: Burr
authors: School of Public Health, Université libre de Bruxelles (ULB), Brussels, Belgium.
authors: Annalisa
authors: A
authors: Casini
authors: Department of Public Health, Ghent University, Ghent, Belgium.
authors: Els
authors: E
authors: Clays
authors: Department of Public Health, Ghent University, Ghent, Belgium.
authors: Dirk
authors: D
authors: De Bacquer
authors: Institute for Medical Sociology, Medical Faculty, University of Düsseldorf, Düsseldorf, Germany.
authors: Nico
authors: N
authors: Dragano
authors: Department of Cardiology, West-German Heart Center Essen, University Duisburg-Essen, Essen, Germany.
authors: Raimund
authors: R
authors: Erbel
authors: TNO, Hoofddorp, Netherlands.
authors: Goedele A
authors: GA
authors: Geuskens
authors: Department of Epidemiology and Public Health, University College London, London, UK.
authors: Mark
authors: M
authors: Hamer
authors: TNO, Hoofddorp, Netherlands.
authors: Wendela E
authors: WE
authors: Hooftman
authors: TNO, Hoofddorp, Netherlands.
authors: Irene L
authors: IL
authors: Houtman
authors: Institute for Medical Informatics, Biometry, and Epidemiology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany.
authors: Karl-Heinz
authors: KH
authors: Jöckel
authors: School of Public Health, Université libre de Bruxelles (ULB), Brussels, Belgium.
authors: France
authors: F
authors: Kittel
authors: Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden.
authors: Anders
authors: A
authors: Knutsson
authors: Department of Public Health, University of Helsinki, Helsinki, Finland.
authors: Markku
authors: M
authors: Koskenvuo
authors: Institute for Medical Sociology, Medical Faculty, University of Düsseldorf, Düsseldorf, Germany.
authors: Thorsten
authors: T
authors: Lunau
authors: National Research Centre for the Working Environment, Copenhagen, Denmark.
authors: Ida E H
authors: IE
authors: Madsen
authors: Unit of Social Medicine, Frederiksberg University Hospital, Copenhagen, Denmark.
authors: Martin L
authors: ML
authors: Nielsen
authors: Stress Research Institute, Stockholm University, Stockholm, Sweden; Department of Psychology, Umeå University, Umeå, Sweden.
authors: Maria
authors: M
authors: Nordin
authors: Finnish Institute of Occupational Health, Helsinki, Tampere and Turku, Finland.
authors: Tuula
authors: T
authors: Oksanen
authors: The Danish National Centre for Social Research, Copenhagen, Denmark.
authors: Jan H
authors: JH
authors: Pejtersen
authors: Finnish Institute of Occupational Health, Helsinki, Tampere and Turku, Finland.
authors: Jaana
authors: J
authors: Pentti
authors: National Research Centre for the Working Environment, Copenhagen, Denmark; Department of Public Health and Department of Psychology, University of Copenhagen, Copenhagen, Denmark.
authors: Reiner
authors: R
authors: Rugulies
authors: Finnish Institute of Occupational Health, Helsinki, Tampere and Turku, Finland; Department of Psychology, University of Turku, Turku, Finland.
authors: Paula
authors: P
authors: Salo
authors: Department of Epidemiology and Public Health, University College London, London, UK.
authors: Martin J
authors: MJ
authors: Shipley
authors: Institute for Medical Sociology, Medical Faculty, University of Düsseldorf, Düsseldorf, Germany.
authors: Johannes
authors: J
authors: Siegrist
authors: Department of Epidemiology and Public Health, University College London, London, UK.
authors: Andrew
authors: A
authors: Steptoe
authors: Department of Public Health, University of Turku, Turku, Finland; Folkhälsan Research Center, Helsinki, Finland; University of Skövde, Skövde, Sweden.
authors: Sakari B
authors: SB
authors: Suominen
authors: Stress Research Institute, Stockholm University, Stockholm, Sweden.
authors: Töres
authors: T
authors: Theorell
authors: Finnish Institute of Occupational Health, Helsinki, Tampere and Turku, Finland; Department of Public Health, University of Turku, Turku, Finland; Turku University Hospital, Turku, Finland.
authors: Jussi
authors: J
authors: Vahtera
authors: Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden.
authors: Peter J M
authors: PJ
authors: Westerholm
authors: Stress Research Institute, Stockholm University, Stockholm, Sweden.
authors: Hugo
authors: H
authors: Westerlund
authors: Centre for Public Health, Queen's University Belfast, Belfast, UK.
authors: Dermot
authors: D
authors: O'Reilly
authors: Department of Epidemiology and Public Health, University College London, London, UK; Institute for Social and Economic Research, University of Essex, Colchester, UK.
authors: Meena
authors: M
authors: Kumari
authors: Department of Epidemiology and Public Health, University College London, London, UK; Centre for Cognitive Ageing and Cognitive Epidemiology and Alzheimer Scotland Dementia Research Centre, University of Edinburgh, Edinburgh, UK.
authors: G David
authors: GD
authors: Batty
authors: Department of Epidemiology and Public Health, University College London, London, UK; School of Community and Social Medicine, University of Bristol, Bristol, UK.
authors: Jane E
authors: JE
authors: Ferrie
authors: Finnish Institute of Occupational Health, Helsinki, Tampere and Turku, Finland.
authors: Marianna
authors: M
authors: Virtanen
mesh_terms: D000367:Age Factors; D003327:Coronary Disease / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012306:Risk; D012307:Risk Factors; D012737:Sex Factors; D012959:Socioeconomic Factors; D020521:Stroke / Q000453:epidemiology / Q000209:etiology*; D014940:Work Schedule Tolerance