title: Job strain and the risk of inflammatory bowel diseases: individual-participant meta-analysis of 95,000 men and women.
abstract: OBJECTIVE
  Many clinicians, patients and patient advocacy groups believe stress to have a causal role in inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis. However, this is not corroborated by clear epidemiological research evidence. We investigated the association between work-related stress and incident Crohn's disease and ulcerative colitis using individual-level data from 95,000 European adults.
  
  
  METHODS
  We conducted individual-participant data meta-analyses in a set of pooled data from 11 prospective European studies. All studies are a part of the IPD-Work Consortium. Work-related psychosocial stress was operationalised as job strain (a combination of high demands and low control at work) and was self-reported at baseline. Crohn's disease and ulcerative colitis were ascertained from national hospitalisation and drug reimbursement registers. The associations between job strain and inflammatory bowel disease outcomes were modelled using Cox proportional hazards regression. The study-specific results were combined in random effects meta-analyses.
  
  
  RESULTS
  Of the 95,379 participants who were free of inflammatory bowel disease at baseline, 111 men and women developed Crohn's disease and 414 developed ulcerative colitis during follow-up. Job strain at baseline was not associated with incident Crohn's disease (multivariable-adjusted random effects hazard ratio: 0.83, 95% confidence interval: 0.48, 1.43) or ulcerative colitis (hazard ratio: 1.06, 95% CI: 0.76, 1.48). There was negligible heterogeneity among the study-specific associations.
  
  
  CONCLUSIONS
  Our findings suggest that job strain, an indicator of work-related stress, is not a major risk factor for Crohn's disease or ulcerative colitis.
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland.
authors.forename: Katriina
authors.initials: K
authors.lastname: Heikkilä
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, Denmark.
authors.forename: Ida E H
authors.initials: IE
authors.lastname: Madsen
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland.
authors.forename: Solja T
authors.initials: ST
authors.lastname: Nyberg
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden ; School of Health Sciences, Jönköping University, Jönköping, Sweden ; Stress Research Institute, Stockholm University, Stockholm, Sweden.
authors.forename: Eleonor I
authors.initials: EI
authors.lastname: Fransson
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland.
authors.forename: Kirsi
authors.initials: K
authors.lastname: Ahola
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Alfredsson
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, Denmark.
authors.forename: Jakob B
authors.initials: JB
authors.lastname: Bjorner
authors.affiliation: Department of Occupational and Environmental Medicine, Bispebjerg University Hospital, Copenhagen, Denmark.
authors.forename: Marianne
authors.initials: M
authors.lastname: Borritz
authors.affiliation: Federal Institute for Occupational Safety and Health (BAuA), Berlin, Germany.
authors.forename: Hermann
authors.initials: H
authors.lastname: Burr
authors.affiliation: Institute for Medical Sociology, Medical Faculty, University of Düsseldorf, Düsseldorf, Germany.
authors.forename: Nico
authors.initials: N
authors.lastname: Dragano
authors.affiliation: School of Community and Social Medicine, University of Bristol, Bristol, United Kingdom ; Department of Epidemiology and Public Health, University College London, London, United Kingdom.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Ferrie
authors.affiliation: Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Knutsson
authors.affiliation: Department of Public Health, University of Helsinki, Helsinki, Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Koskenvuo
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland.
authors.forename: Aki
authors.initials: A
authors.lastname: Koskinen
authors.affiliation: Department of Occupational and Environmental Medicine, Bispebjerg University Hospital, Copenhagen, Denmark.
authors.forename: Martin L
authors.initials: ML
authors.lastname: Nielsen
authors.affiliation: Department of Psychology, Umeå University, Umeå, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Nordin
authors.affiliation: The Danish National Centre for Social Research, Copenhagen, Denmark.
authors.forename: Jan H
authors.initials: JH
authors.lastname: Pejtersen
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Tampere and Turku, Finland.
authors.forename: Jaana
authors.initials: J
authors.lastname: Pentti
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, Denmark ; Department of Public Health and Department of Psychology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Reiner
authors.initials: R
authors.lastname: Rugulies
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Tampere and Turku, Finland.
authors.forename: Tuula
authors.initials: T
authors.lastname: Oksanen
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, United Kingdom.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Shipley
authors.affiliation: Folkhälsan Research Center, Helsinki, Finland ; Department of Public Health, University of Turku, Turku, Finland ; Nordic School of Public Health, Göteborg, Sweden.
authors.forename: Sakari B
authors.initials: SB
authors.lastname: Suominen
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, Sweden.
authors.forename: Töres
authors.initials: T
authors.lastname: Theorell
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland.
authors.forename: Ari
authors.initials: A
authors.lastname: Väänänen
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Tampere and Turku, Finland ; Department of Public Health, University of Turku, Turku, Finland.
authors.forename: Jussi
authors.initials: J
authors.lastname: Vahtera
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland.
authors.forename: Marianna
authors.initials: M
authors.lastname: Virtanen
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, Sweden.
authors.forename: Hugo
authors.initials: H
authors.lastname: Westerlund
authors.affiliation: Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden.
authors.forename: Peter J M
authors.initials: PJ
authors.lastname: Westerholm
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, United Kingdom ; Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edingurgh, United Kingdom.
authors.forename: G David
authors.initials: GD
authors.lastname: Batty
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, United Kingdom ; Inserm U1018, Centre for Research in Epidemiology and Population Health, Villejuif, France.
authors.forename: Archana
authors.initials: A
authors.lastname: Singh-Manoux
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland ; Department of Epidemiology and Public Health, University College London, London, United Kingdom.
authors.forename: Mika
authors.initials: M
authors.lastname: Kivimäki
mesh_terms: D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000453:epidemiology* / Q000523:psychology*; D008297:Male; D012306:Risk; D013315:Stress, Psychological; D014937:Work / Q000523:psychology*