Background Mental functioning is reported as an important outcome measure in patients with Rheumatoid Arthritis (RA). Patients show lower mental functioning scores than the general population (1). A factor that has great impact on the overall health outcomes is comorbidity (2). Both somatic and depression comorbidity are common in patients with RA. Investigating the influence of comorbidity on mental functioning provides clinicians long term information for a particular patient.
Objectives To asses the long term association of somatic and depression comorbidity and mental functioning in patients with RA.
Methods Longitudinal data over a period of eleven years were collected among 882 patients with RA of varying disease duration. Patient reported outcomes were collected in 1997, 1998, 1999, 2002 and 2008. Mental functioning was measured with the Mental Component Scale of the Short Form-36 Health Survey. Somatic comorbidity was measured by a self administered questionnaire including 13 chronic diseases. Depression comorbidity was measured with the Center for Epidemiologic Depression Scale. We distinguished four groups of patients based on comorbidity at baseline: patients 1) without comorbidity 2) with only somatic comorbidity 3) with only depression comorbidity and 4) with both somatic and depression comorbidity. The influence of comorbidity at baseline on mental functioning over time was investigated in a longitudinal analysis.
Results 882 patients responded to the questionnaire, of whom 78% were women. The mean age of the patients at baseline was 59.3 (SD 14.8) years and the mean disease duration was 8.9 (SD 9.9) years. For the total group of patients with RA mental functioning stayed stable over time. There was no difference in mental functioning between patients without comorbidity and patients with somatic comorbidity. Patients without comorbidity at baseline had better mental functioning at all time points than patients with depression comorbidity and patients with both somatic and depression comorbidity (p<0.01). However, the difference in mental functioning between patients without comorbidity and patients with both somatic and depression comorbidity decreased between baseline and eleven years follow up (p<0.01).
Conclusions Depression comorbidity and the combination of both somatic and depression comorbidity was negatively associated with mental functioning and this association was present during eleven years follow up. Because of its long term consequences, early screening for depression comorbidity in RA would be recommended, so additional intervention can start early in the disease process to reduce the negative effects of this comorbidity.
Uhlig T, Loge JH, Kristiansen IS, Kvien TK. Quantification of reduced health-related quality of life in patients with rheumatoid arthritis compared to the general population. J Rheumatol 2007; 34(6):1241-1247.
Gabriel SE, Michaud K. Epidemiological studies in incidence, prevalence, mortality, and comorbidity of the rheumatic diseases. Arthritis Res Ther 2009; 11(3):229.
Disclosure of Interest None Declared
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