Changes in frailty and its association with dementia risk in four prospective cohorts.

BackgroundPrevious studies found baseline frailty is a key risk factor for dementia, but changes in frailty during follow-up were less considered. Clarifying the impact of frailty change may help prevent or delay dementia.ObjectiveThis study investigates frailty changes and their link to dementia risk.MethodsIn this cohort study, we used four prospective cohorts: Health and Retirement Study (HRS), English Longitudinal Study of Ageing (ELSA), China Health and Retirement Longitudinal Study (CHARLS), and Ageing and Retirement in Europe (SHARE). The Fried frailty phenotype classified participants as: robust, pre-frail, and frail. Dementia was defined as those with a combination of cognitive and functional impairment, or those who had self-reported doctor-diagnosed dementia. Cox proportional-hazards model was used to examine the association of changes in frailty with dementia risk.ResultsAfter exclusions, 28,679 participants from an initial sample of 134,834 were included in the analysis. Compared with stable robust participants, those progressing to pre-frail/frail had higher dementia risk (HRS, HR 2.05, 95% CI 1.54-2.72; ELSA, HR 2.24, 95% CI 1.20-4.17; CHARLS, HR 2.85, 95% CI 1.42-5.73; SHARE, HR 1.78, 95% CI 1.34-2.37). Conversely, frail participants who recovered to robust/pre-frail had lower risk than stable frail.ConclusionsAs the frailty status advances, the risks of incident dementia escalate. In contrast, when the frailty status recovers, the risks of incident dementia reduce.