What factors mediate the inter-relationship between frailty and pain in cognitively and functionally sound older adults? A prospective longitudinal ageing cohort study in Taiwan.

OBJECTIVES: The main aim was to investigate the complex inter-relationship between frailty and pain, and the mediating roles of cognitive function, morbidity and mood in this nexus.

DESIGN: A cross-sectional analysis.

SETTING: A prospective community-dwelling population-based cohort.

PARTICIPANTS: 1682 adults age ≥50 years without evident cognitive or functional impairment, or history of cancer.

PRIMARY AND SECONDARY OUTCOME MEASURES: The mediating effect of depression, cognitive function and comorbidity on the nexus between pain and frailty among older and middle-aged adults.

RESULTS: The pain score among older subjects (≥65 years), increased with the degree of frailty (robust=0.96±0.82; pre-frail=1.13±0.86; frail=1.63±1.02; P<0.001); multivariate analysis gave the same result, while moderate pain was associated with frailty in older subjects (OR=3.00, 95% CI 1.30 to 6.60). Conversely, pain and frailty among middle-aged subjects (aged 50-64 years) did not appear to be significantly related; in mediation analysis, pain exerted an indirect effect on frailty via depression (indirect effect=0.03, 95% CI 0.01 to 0.07), while neither cognitive function nor comorbidity had any significant effect in mediating the relationship between pain and frailty.

CONCLUSION: In cognitively and functionally sound community-dwelling adults aged ≥50 years, moderate pain was related to frailty in those older than 65 years, but not younger ones. Besides the direct influence of pain on frailty, depression partially mediated the pain-frailty nexus. The mechanism by which depression influences pain and frailty requires further investigation.