Association of body age and multiorgan ages with cognitive decline in older adults: a nationwide longitudinal study

Background: It is unknown whether the relationship between ageing of different organs and cognitive decline varies in older adults. Objectives: This study investigated the association of body ageing and organ-specific ageing with cognitive decline, and whether this relationship was strengthened by hearing loss. Methods: The study included older adults free from cognitive impairment, drawn from the Chinese Longitudinal Healthy Longevity Survey. Organ-specific ages were estimated using the support vector machines. The age gap and ageing rate were calculated. Cognitive function was assessed at each visit using the Mini-mental State Examination, and a linear mixed-effects model was employed for analysis. Results: Over a median follow-up period of 6 years, of 1003 older adults (mean age 80.8 +/- 10.9 years, 47.7% female) included, 187 (18.6%) experienced cognitive impairment. Compared to individuals with biological younger for body, musculoskeletal system and immune system, biological older (age gap > 0) was associated with faster cognitive decline (beta(body) = -0.229, 95% confidence interval [CI]: -0.435, -0.023; beta(muscle) = -0.294, 95% CI: -0.500, -0.088; beta(immune) = -0.246, 95% CI: -0.452, -0.041), but not for cardiometabolic and renal systems. A linear positive dose-response association between age gap and cognitive impairment was uniquely observed for musculoskeletal system, whereas null associations for other organ systems. Moreover, higher ageing rates of body and musculoskeletal system were associated with faster cognitive decline. In the joint exposure analysis, hearing loss significantly strengthened the body age gap/ageing rate-cognitive decline association. Conclusions: Advanced biological ageing of the body, musculoskeletal system and immune system, particularly in the presence of hearing loss, accelerates cognitive decline.