Co-morbidities increase the risk of disability pension among MS patients: a population-based nationwide cohort study

BACKGROUND Multiple sclerosis (MS) is a chronic and often disabling disease. In 2005, 62% of the MS patients in Sweden aged 16-65 years were on disability pension. The objective of this study is to investigate whether the presence of common co-morbidities increase MS patients' risk for disability pension. METHODS This population-based cohort study included 4 519 MS patients and 4 972 174 non-MS patients who in 2005 were aged 17-64 years, lived in Sweden, and were not on disability pension. Patients with MS were identified in the nationwide in- and outpatient registers, while four different registers were used to construct three sets of measures of musculoskeletal, mental, and cardiovascular disorders. Time-dependent proportional hazard models with a five-year follow up were performed, adjusting for socio-demographic factors. RESULTS All studied disorders were elevated among MS patients, regardless of type of measure used. MS patients with mental disorders had a higher risk for disability pension than MS patients with no such co-morbidities. Moreover, mental disorders had a synergistic influence on MS patients' risk for disability pension. These findings were also confirmed when conducting sensitivity analyses. Musculoskeletal disorders appeared to increase MS patients' risk for disability pension. The results with regard to musculoskeletal disorders' synergistic influence on disability pension were however inconclusive. Cardiovascular co-morbidity had no significant influence on MS-patients' risk for disability pension. CONCLUSIONS Co-morbidities, especially mental disorders, significantly contribute to MS patients' risk of disability pension, a finding of relevance for MS management and treatment.