Functional limitations in functional somatic syndromes and well-defined medical diseases. Results from the general population cohort LifeLines.

OBJECTIVE: Functional somatic syndromes (FSS), defined as physical syndromes without known underlying organic pathology, are sometimes regarded as less serious conditions than well-defined medical diseases (MD). The aims of this study were to evaluate functional limitations in FSS, and to compare the results to MD patients with the same core symptoms.

METHODS: This study was performed in 89,585 participants (age: 44.4±12.4 years, 58.5% female) of the general-population cohort LifeLines. Quality of Life (QoL) and work participation were examined as indicators of functional limitations. QoL was assessed with two summary scales of the RAND-36: the physical component summary (PCS) and the mental component summary (MCS). Work participation was assessed with a self-reported questionnaire. QoL and work participation were compared between FSS and MD patients, using Chi-squared tests and ANCOVA-analyses, adjusted for age, sex, educational level, and mental disorders.

RESULTS: Of the participants, 11.0% (n=9861) reported a FSS, and 2.7% (n=2395) reported a MD. Total QoL, PCS and MCS were significantly lower in all separate FSS and MD compared to controls (P≤.001). Clinically relevant differences in QoL were found between chronic fatigue syndrome and multiple sclerosis patients, and between fibromyalgia syndrome and rheumatoid arthritis patients. Compared to controls, FSS and MD patients reported a comparably reduced working percentage, increased sick absence, early retirement due to health-related reasons, and disability percentage (P≤.001).

CONCLUSION: Functional limitations in FSS patients are common, and as severe as those in patients with MD when looking at QoL and work participation, emphasizing that FSS are serious health conditions.