title: Persistent smoking as a predictor of disability pension due to musculoskeletal diagnoses: a 23 year prospective study of Finnish twins.
abstract: OBJECTIVE
  To investigate whether stability or changes in smoking predict disability pension (DP) due to low back diagnoses (LBD) and musculoskeletal diagnoses (MSD) after taking familial confounding into account using a co-twin design.
  
  
  METHODS
  Longitudinal smoking patterns and multiple covariates in a population-based cohort of 17,451 Finnish twins (6959 complete pairs) born before 1958 were surveyed through questionnaires in 1975 and 1981. The outcome data were collected from the national pension registers until the end of 2004. Cox proportional hazards regression models were used for statistical analyses.
  
  
  RESULTS
  Disability pension due to low back diagnoses was granted to 408 individuals and disability pension due to musculoskeletal diagnoses to 1177 individuals during the follow-up of 23 years. Being a persistent smoker (current smoker both 1975 and 1981) predicted a significantly increased risk for disability pension (hazard ratio 1.69, 95% confidence interval 1.46, 1.97) compared to those individuals who had never smoked. The association remained when several confounding factors, including familial factors, were taken into account.
  
  
  CONCLUSIONS
  Persistent smoking predicts early disability pension due to musculoskeletal diagnoses and low back diagnoses independently from numerous confounding factors, including familial effects shared by the co-twins.
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, Finland. Electronic address: annina.ropponen@ttl.fi.
authors.forename: Annina
authors.initials: A
authors.lastname: Ropponen
authors.forename: Tellervo
authors.initials: T
authors.lastname: Korhonen
authors.forename: Pia
authors.initials: P
authors.lastname: Svedberg
authors.forename: Markku
authors.initials: M
authors.lastname: Koskenvuo
authors.forename: Karri
authors.initials: K
authors.lastname: Silventoinen
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
mesh_terms: D000367:Age Factors; D006233:Persons with Disabilities / Q000706:statistics & numerical data*; D004200:Diseases in Twins / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D008297:Male; D009140:Musculoskeletal Diseases / Q000453:epidemiology / Q000209:etiology*; D010415:Pensions / Q000706:statistics & numerical data; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D011795:Surveys and Questionnaires
keywords: Disability pension; Musculoskeletal disorders; Prospective design; Sickness absence; Smoking