The burden of symptoms predicts early retirement: a twin cohort study on fibromyalgia-associated symptoms

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.

Conclusion: 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.