Impact of self-reported comorbidity on physical and mental health status in early symptomatic osteoarthritis: the CHECK (Cohort Hip and Cohort Knee) study.

Objective: To describe the relationship between comorbidity (absolute number as well as the presence of specific comorbidities) and pain, physical functioning and mental health status of participants with early symptomatic OA of the hip or knee.
Methods: In the Netherlands, a prospective 10-year follow-up study was initiated by the Dutch Arthritis Association in participants with early symptomatic OA of the hip or knee: CHECK (Cohort Hip and Cohort Knee), which consists of 1002 individuals. At baseline, linear regression analysis was used to determine the influence of comorbidity on the outcome variables: Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain, WOMAC physical functioning, Medical Outcomes Study Short Form 36 (SF-36) Physical Component Summary and Mental Component Summary.
Results: Of 979 subjects, 67% reported one or more comorbidities. After controlling for age, gender, social status and severity of radiographic OA (Kellgren and Lawrence score), back disorders have the largest effect on WOMAC pain and physical functioning, and one of the largest effects on physical status of SF-36, besides obesity. Mental status was negatively influenced by the additional presence of duodenal ulcer, thyroid disease, and migraine or chronic headache.
Conclusion: In early stage of OA, the presence of additional problems in the musculoskeletal system and of obesity have a negative effect on pain and physical health status. Also mental status is affected in early symptomatic OA by the presence of specific comorbidities. Comorbidity should be assessed and treated to improve the burden of illness in patients with early symptomatic OA.