title: Sleep patterns as predictors for disability pension due to low back diagnoses: a 23-year longitudinal study of Finnish twins.
abstract: OBJECTIVE
  Impaired sleep patterns are known to be associated with many chronic conditions and ultimately they may lead to permanent work incapacity. Less is known about the associations between sleep patterns and cause-specific disability pensions, such as low back diagnoses, or whether familial factors (genetics and family environment) can affect the associations. The objective of this study was to investigate sleep patterns as predictors of disability pension due to low back diagnoses with a 23-year follow-up.
  
  
  METHODS
  A prospective cohort study with comprehensive mailed questionnaires about sleep patterns, e.g., quality and length of sleep in 1975 and 1981. Follow-up from the national disability pension register data until 2004.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  There were 18,979 individuals (7,722 complete twin pairs) born before 1958.
  
  
  RESULTS
  Cox proportional hazards regression was used to calculate hazard ratios (HR) with 95% confidence intervals (95% CI). Disability pension due to low back diagnoses had been granted to 467 individuals during the follow-up. Sleeping moderately well (HR 1.25; 95% CI 1.02, 1.53), or fairly poorly/poorly (HR 2.05; 95% CI 1.53, 2.73) at baseline predicted a significantly higher risk for disability pension. Stable patterns of sleeping either fairly well (HR 1.29; 95% CI 1.01, 1.64), or stably fairly poorly/poorly (HR 2.29; 95% CI 1.49, 3.52) between 1975 and 1981 were associated with a higher risk as compared to a stable pattern of sleeping well. Furthermore, a decrease in quality of sleep from 1975 to 1981 was associated (HR 1.34; 95% CI 1.03, 1.76) with an increased risk of disability pension.
  
  
  CONCLUSIONS
  Sleep quality and changes in sleep quality appear to be early predictors for disability pension due to low back diagnoses independently from other confounding factors.
authors.affiliation: School of Medicine, University of Eastern Finland, Kuopio, Finland. annina.ropponen@gmail.com
authors.forename: Annina
authors.initials: A
authors.lastname: Ropponen
authors.forename: Karri
authors.initials: K
authors.lastname: Silventoinen
authors.forename: Christer
authors.initials: C
authors.lastname: Hublin
authors.forename: Pia
authors.initials: P
authors.lastname: Svedberg
authors.forename: Markku
authors.initials: M
authors.lastname: Koskenvuo
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
mesh_terms: D000328:Adult; D006233:Persons with Disabilities / Q000706:statistics & numerical data*; D004200:Diseases in Twins / Q000453:epidemiology; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D008137:Longitudinal Studies; D017116:Low Back Pain / Q000150:complications* / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D010415:Pensions / Q000706:statistics & numerical data*; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors; D012893:Sleep Wake Disorders / Q000150:complications* / Q000453:epidemiology; D011795:Surveys and Questionnaires
keywords: Sleep; disability pension; low back diagnoses; sick leave