title: The burden of symptoms predicts early retirement: a twin cohort study on fibromyalgia-associated symptoms.
abstract: OBJECTIVE
  To assess whether symptoms of fibromyalgia (FM) predict disability retirement or mortality.
  
  
  METHODS
  All Finnish Twin Cohort members and diagnosed FM-patients who had answered the same health questionnaire in 1990-1992 were studied. A sample of 10,608 working aged individuals of the cohort was classified in homogenous groups based on symptom profile with latent class analysis, using a battery of questions addressing FM-associated symptoms validated between FM-patients and twins. This resulted in three classes: no or few symptoms (LC1), some symptoms (LC2), and high load of FM-symptoms (LC3). In a 14-year follow-up, 1990-2004, information on disability retirement was obtained from official pension registers. Further linkage with Population Register Centre data for 1990-2009 yielded information on the vital status of the cohort subjects. Those with malignancies or inflammatory rheumatic diseases were excluded.
  
  
  RESULTS
  Cumulative incidence of early disability retirement was 9.5% among all 8448 individuals (after exclusions), and 26% in LC3. Adjusted hrs for early retirement were 1.0 (reference class) in LC1, 1.5 (95%CI 1.2-1.7) in LC2, and 2.9 (2.4-3.6) in LC3 for all causes and 1.8 (1.4-2.5) in LC2 and 5.0 (3.6-6.9) in LC3 for musculoskeletal disorders. In 173,675 person-years, the high symptom class (LC3) had a 43% (95% CI 17-75%) increased overall mortality risk, which was fully accounted for by adjustment for lifestyle factors, mainly smoking.
  
  
  CONCLUSIONS
  Symptoms associated with FM strongly correlate with early disability retirement. Lifestyle problems associated with high symptom load need prompt management to avoid increased risk of mortality.
authors.affiliation: Helsinki University Central Hospital, Pain Clinic, Department of Anaesthesiology and Intensive Care Medicine, Finland. ritva.markkula@helsinki.fi
authors.forename: Ritva
authors.initials: R
authors.lastname: Markkula
authors.forename: Eija
authors.initials: E
authors.lastname: Kalso
authors.forename: Antti
authors.initials: A
authors.lastname: Huunan-Seppälä
authors.forename: Markku
authors.initials: M
authors.lastname: Koskenvuo
authors.forename: Karoliina
authors.initials: K
authors.lastname: Koskenvuo
authors.forename: Päivi
authors.initials: P
authors.lastname: Leino-Arjas
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
mesh_terms: D000328:Adult; D000368:Aged; D006233:Persons with Disabilities; D004200:Diseases in Twins / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D005356:Fibromyalgia / Q000175:diagnosis* / Q000453:epidemiology; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012179:Retirement; D011795:Surveys and Questionnaires; D014427:Twins