Underlying Factors in the Association between Depressed Mood and Mobility Limitation in Older People

Background: Depressed mood may either precede mobility limitation or follow from mobility limitation. Objective: To compare mood status among people with manifestmobility limitation, those with preclinical mobility limitation and those without mobility limitation and investigate factors explaining the association between depressed mood and mobility limitation. Design: Cross-sectional. Subjects: 645 community-living 75- to 81-year-old people. Methods: Depressed mood was assessed using the Centre for Epidemiologic Studies Depression Scale (CES-D, cut-off score 16); difficulty walking 500 m was assessed by self-report. Those reporting difficulty were categorised as having manifest mobility limitation. Those with no difficulty but reporting task modifications, such as reduced frequency of walking, were categorised as having preclinical mobility limitation. The association between depressed mood and mobility limitation was analysed using logistic regression analysis with gender, age, economic situation, the availability of a confidant, chronic conditions, and widespread pain as covariates. Results: Depressed mood was found in 34% of subjects with manifest mobility limitation, in 26% of those with preclinical mobility limitation, and in 13% of those without mobility limitation. The unadjusted odds ratio for depressed mood was 3.43 (95% CI 2.04–5.76) among subjects with manifest mobility limitation and 2.38 (95% CI 1.52–3.73) among those with preclinical mobility limitation, compared to those without mobility limitation.Adjustment forcovariates reduced the risks to 2.10 (95% CI 1.15–3.82) and 1.99 (95% CI 1.24–3.20), respectively. Widespread pain explained 28% of the increased risk of depressed mood among those with manifest mobility limitation. Conclusion: The dose-response relationship between depressed mood and mobility limitation suggests that both conditions may progress simultaneously and may share aetiology, at least in part. Pain may be an underlying factor in both depressed mood and mobility limitation.