The association between multimorbidity and intrinsic capacity among older adults: The mediating role of frailty

Background Intrinsic capacity(IC) proposed by the World Health Organization(WHO) is the core indicator of healthy aging, directly affecting functional ability and quality of life in older adults. Multimorbidity is an important influencing factor of IC, but the underlying mechanism remains unclear. This study aims to explore the mediating role of frailty in the association between multimorbidity and IC. Methods This population-based cross-sectional study included 468 elderly individuals from community settings and nursing homes in Lianyungang city, Jiangsu Province (the WHO ICOPE Pilot in China).Age, gender, education, marital status, and nursing home residence were assessed at baseline. Multimorbidity was assessed based on clinical experience, the Charlson Comorbidity Index (CCI) and the Cumulative Illness Rating Scale for Geriatrics (CIRS-G). Frailty was evaluated using the FRAIL scale. IC was measured using the WHO ICOPE screening tool (including assessments of cognitive function, motor function, nutritional status, sensory ability, and depression). Binary logistic regression was employed to calculate the associations between multimorbidity, frailty, and IC. Mediation analysis was conducted to explore the mediating role of frailty in the multimorbidity–IC relationship. Results After adjusting for all covariates (age, gender, marital status, education level and community or nursing home), multimorbidity was found to be positively correlated with IC. Each additional multimorbidity increased the risk of impaired IC by 62.7%. Subgroup analyses revealed that the multimorbidity and IC relationship was robust. The direct effect of multimorbidity on IC was significant (β = 0.154, 95% CI: 0.064, 0.243, p < 0.001). Frailty significantly mediated the relationship between multimorbidity and IC (β = 0.058, 95% CI: 0.029, 0.092, p < 0.001; mediation proportion: 27.5%). The total effect of multimorbidity on IC was also significant (β = 0.211, 95% CI: 0.123, 0.300, p < 0.001). Conclusions The number of multimorbidities was positively associated with IC among older adults, and frailty mediated this association. These findings highlight the need to integrate the management of multimorbidity and frailty to prevent and delay the IC impairments among older adults.