Background Body mass index (BMI) and depression are positively associated with each other (Rosemann et al. 2008), and positively associated with pain and activity limitations in knee osteoarthritis (OA) patients (Dekker et al. 2009). There is growing evidence that metabolic factors are involved in both the development of overweight and depression (McIntyre et al. 2007). This raises the question whether BMI and depression are related to knee pain and activity limitations independently of each other.
Objectives To establish if BMI and depression are independently associated with knee pain and activity limitations in knee OA patients.
Methods A cross-sectional study was conducted in a sample of 304 participants with knee OA from the Amsterdam Osteoarthritis Cohort. All patients fulfilled the American College of Rheumatology (ACR) clinical criteria for knee OA. Depression was measured with the Hospital Anxiety and Depression Scale. Pain was measured with a numeric rating scale for knee pain during the last week, and activity limitations were measured with the Western Ontario and McMaster Universities Osteoarthritis Index and the timed get up and go test. Multivariable regression analyses were performed with BMI and depression as independent variables, and pain and activity limitations as dependent variables. Regression models with only BMI or only depression as independent variable were compared with regression models with both BMI and depression as independent variables. All analyses were adjusted for age, gender, civil status, educational level and comorbidity count.
Results BMI and depression were independently associated with knee pain. After adjustment for each other the regression coefficients (Bs) of BMI and depression changed with 20.5% and 16.4% respectively, and were still significantly associated with knee pain (p≤0.01). BMI and depression were independently associated with both self-reported and performance-based activity limitations (p≤0.01). After adjustment for each other the Bs of BMI and depression changed with 10.3% and 27.9% in the analyses with self-reported activity limitations as dependent variable, and with 4.7% and 40.6% in the analysis with performance-based activity limitations as dependent variable.
Conclusions The association between overweight and knee pain and activity limitations is not explained by depression, and the association between depression and knee pain and activity limitations is not explained by overweight. Both BMI and depression are independently associated with knee pain and activity limitations. As a consequence, in treating patients with knee OA, overweight and depression should both be targeted.
Disclosure of Interest None Declared
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