title: Physical work load and psychological stress of daily activities as predictors of disability pension due to musculoskeletal disorders.
abstract: OBJECTIVE
  Physical work loading and psychological stress commonly co-occur in working life, hence potentially having an interrelationship that may affect work incapacity. This prospective cohort study aimed to investigate the effect of stability and change in physical work loading and stress on the risk of disability pension (DP) due to musculoskeletal diagnoses (MSD), while accounting for familial confounding in these associations.
  
  
  METHODS
  Data on 12,455 twins born before 1958 were surveyed of their physical work loading and psychological stress of daily activities in 1975 and 1981. The follow-up data was collected from pension registers until 2004. Cox proportional hazards regression models were used.
  
  
  RESULTS
  During the follow up, 893 participants were granted DP due to MSD. Stable high (hazard ratio, HR, 2.21), but also increased physical work loading (HR 2.05) and high psychological stress (HR 2.22) were associated with increased risk for DP, and had significant interaction (p=0.032). The associations were confirmed when accounting for several confounding factors.
  
  
  CONCLUSIONS
  Stable high but also increased physical work loading and psychological stress of daily activities between two timepoints with 6 years apart confirms their predictive role for an increased risk of DP. Both physical work loading and psychological stress seem to be independent from various confounding factors hence suggesting direct effect on risk for DP providing potential for occupational health care to early identification of persons at risk.
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland annina.ropponen@ttl.fi.
authors.forename: Annina
authors.initials: A
authors.lastname: Ropponen
authors.affiliation: Division of Insurance Medicine, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Pia
authors.initials: P
authors.lastname: Svedberg
authors.affiliation: Department of Public Health, Hjelt Institute, University of Helsinki, Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Koskenvuo
authors.affiliation: Population Research Unit, Department of Sociology, University of Helsinki, Finland.
authors.forename: Karri
authors.initials: K
authors.lastname: Silventoinen
authors.affiliation: Department of Public Health, Hjelt Institute, University of Helsinki, Finland Department of Mental Health and Substance Abuse Services, National Institute for Health and Welfare, Finland Institute for Molecular Medicine, University of Helsinki, Finland.
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology*; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D006801:Humans; D018868:Insurance, Disability / Q000706:statistics & numerical data*; D009140:Musculoskeletal Diseases / Q000453:epidemiology*; D009784:Occupational Diseases / Q000453:epidemiology*; D010415:Pensions / Q000706:statistics & numerical data*; D011446:Prospective Studies; D018570:Risk Assessment; D013315:Stress, Psychological / Q000453:epidemiology*; D016526:Workload
keywords: Musculoskeletal diseases; prospective studies; psychological; sick leave; stress; work