Association between frailty and multisite chronic pain in middle-aged and older adults

The corrected modified frailty index (CMFI), based on the accumulation of multidimensional health impairments, provides a more comprehensive reflection of an individual's overall frailty. Although chronic pain is associated with aging, its relationship with CMFI, in population-based cohorts remains unclear. This cross-sectional study included 5821 participants aged ≥45 years from the 2011 baseline wave of the China Health and Retirement Longitudinal Study. Chronic pain, including low back pain, multisite pain, and the number of pain sites, was assessed via self-reported questionnaires. Frailty was assessed using the CMFI. Weighted logistic regression models, restricted cubic splines, and mediation analyses were employed to investigate associations and the potential roles of depression and C-reactive protein. Analysing data from 5281 participants, higher CMFI was strongly associated with increased risk and burden of chronic pain. Compared with the lowest quartile, the highest CMFI quartile showed significantly higher risks of low back pain (odds ratio = 11.6, 95% confidence interval [CI]: 8.96-15.0), multisite pain (odds ratio = 17.0, 95% CI: 13.1-22.2), and a greater number of pain sites (incidence rate ratio = 11.5, 95% CI: 8.90-14.8). Associations varied across subgroups defined by age, education, and residence. Depression mediated approximately 30% of these associations. Higher CMFI levels were associated with greater risk and burden of chronic pain, with depression potentially accounting for part of the association. These findings highlight the importance of incorporating mental health assessments into frailty and pain management among the middle-aged and older adults included in China Health and Retirement Longitudinal Study.