Physical comorbidity in patients with multiple functional somatic syndromes. A register-based case-control study.

BACKGROUND:Patients with multiple functional somatic syndromes show markedly reduced functioning and numerous somatic symptoms that cannot be explained by conventionally-defined physical disease. Whilst the comorbidity of functional somatic syndromes with mental disorders is well-known, knowledge about physical comorbidity and mortality is scarce. AIM:To compare number of physical diseases between patients with multiple functional somatic syndromes (operationalized as multi-organ bodily distress syndrome) and the general population with regard to: 1) All conventionally-defined physical diseases, and 2) Severe mortality-associated physical diseases. MATERIALS AND METHODS:Patients with multiple functional somatic syndromes (n=239) were compared with age- and gender-matched population-based controls (n=5975). The number of physical diseases during a four-year period was estimated by means of registered ICD-10 codes in relation to hospital admissions and ambulatory care. We counted individual diagnoses indicating conventionally-defined physical disease based on a previously developed diagnosis sorting algorithm and an additional clinical evaluation, excluding unspecific (symptom) diagnoses and functional somatic syndromes. An updated version of Charlson Comorbidity Index (CCI12) was used to estimate severe, mortality-associated physical diseases. RESULTS:Patients with multiple functional somatic syndromes had an increased number of conventionally-defined physical disease compared to controls (Ratio: 2.17, 95% CI: 1.96-2.41). Groups were similar as regards CCI12 (P=0.55). CONCLUSIONS:Patients with multiple functional somatic syndromes showed substantial physical comorbidity. Their burden of severe, mortality-associated physical diseases was comparable to the general population. Further research is needed to clarify the nature, clinical significance, and long-term consequences of the comorbid physical diseases.