Association between systemic inflammation and activities of daily living disability among Chinese elderly individuals: the mediating role of handgrip strength

Background Aging is accompanied by chronic low-grade inflammation (inflammaging), which is a risk factor for low handgrip strength (HGS) and activities of daily living (ADL) disability. Aims To explore the association between C-reactive protein (CRP) and ADL disability in Chinese elderly individuals and to further evaluate the mediating role of HGS in this association. Methods We used data from the China Health and Retirement Longitudinal Study (CHARLS) that were collected in 2015. A total of 3601 elderly individuals aged >= 60 years were included. Baron and Kenny's causal steps method was used to explore the possible mediating role of HGS in the associations between CRP and ADL disability. Karlson-Holm-Breen method was further applied to decompose total effect into direct effect and indirect effect via HGS. Subgroup analysis was conducted by sex and age. Results A high level of CRP (>= 3 mg/L) was significantly associated with ADL disability after adjustment for covariates (OR = 1.50, 95% CI = 1.17-1.94). After introducing HGS into the model, the risk estimate was reduced but still significant (OR = 1.40, 95% CI = 1.08-1.81). The proportional mediation through HGS was 14.71%. Similar results were observed in both sexes and in participants aged < 70 years. Conclusion CRP was positively associated with the risk of ADL disability in Chinese elderly individuals, and this association was mediated by HGS. Improving muscle strength in combination with anti-inflammatory treatment may have a beneficial effect to maintain ADL ability. Further randomized controlled trials on this topic are necessary.