To describe the extent of somatic comorbid conditions in patients with rheumatoid arthritis (RA) and to assess the influence of comorbidity on health-related quality of life (HRQOL).
A 2-year followup study on health and HRQOL was conducted among 679 patients with RA with varying disease duration. Data were collected by means of questionnaires and clinical examinations at baseline and at 2-year followup. Comorbidity was measured by a self-administered questionnaire including 17 chronic diseases. HRQOL was assessed with the RAND-36. The effect of incident comorbid conditions on HRQOL was investigated with linear regression analyses.
At least one comorbid condition was reported at baseline by 56% of patients. Significant differences in prevalence rates with the Dutch population were found. The effect of comorbidity on HRQOL depended on both the type of comorbid condition and the dimension of HRQOL. Gastrointestinal (GI) diseases, cancer, dizziness with falling (and less severe chronic pulmonary disease and heart complaints) resulted in significant adverse changes in HRQOL. For the other conditions under study no influence could be detected.
Our results indicate that measuring comorbidity by a summary count, assuming an overall equally large effect of each comorbid condition, may not reveal the real effect. With respect to clinical practice, our results emphasize the relevance for health care providers to be aware of specific comorbid conditions exposing patients with RA at risk for additional impairment of HRQOL, and to be aware of interactions with RA that may be unique.