(i) To determine the association between the presence of comorbidities and severity of pain and physical dysfunction in people with knee and/or hip osteoarthritis; (ii) to explore associations between specific comorbidities (cardiac disease and/or hypertension, diabetes, depression, and back pain) and symptom severity.
Studies were identified through systematic searches in four electronic databases and grey literature, and, subsequently, methodologically appraised. Eligible citations entailed cross-sectional or longitudinal studies as well as randomised controlled trials providing data of a direct association between comorbidity presence and the severity of self-reported and/or performance-based symptoms of pain and/or physical functioning, in people with knee and/or hip osteoarthritis. We performed random-effects meta-analysis if at least two citations of low-to-moderate risk of bias were available. The quality of the body of evidence was determined using Cochrane-recommended methods.
Of all eligible citations (n = 26), 17 studies were entered in meta-analysis. Moderate quality evidence revealed an association between having ≥1 general comorbidity and worsening of pain (regression coefficient (95% confidence interval (CI)): 0.18 (95% CI: 0.14,0.22)) and/or performance-based physical functioning (0.20 (95% CI: 0.10,0.29)). The presence of cardiac disease and/or hypertension (self-reported: 0.08 (95% CI: 0.01,0.16); performance-based: 0.11 (95% CI: 0.02,0.20)), or back pain (self-reported: 0.12 (95% CI: 0.04,0.20)) predicted deteriorated physical functioning. Co-existing diabetes was associated with worse pain (0.10 (95% CI: 0.02,0.17)). Other findings were non-significant and/or the evidence of poor quality.
Greater comorbidity burden contributes to worse pain and performance-based physical function in people with knee and/or hip osteoarthritis. Suffering comorbid cardiac disease including hypertension, back pain or diabetes may have differential effects on symptom severity.