Trajectories of frailty, grip strength and gait speed preceding dementia: a nested case-control study.

BACKGROUND: Functional decline may be an early indicator of dementia. This study examined the trajectories of frailty, grip strength, and gait speed over the 11 years prior to dementia, compared to matched individuals without dementia. METHODS: A total of 1092 dementia cases were matched on age, sex and education to 4368 controls from a cohort of community-dwelling older adults recruited in Australia and the USA, aged 65 years or above at recruitment. Frailty was characterised by a deficit-accumulation index involving 67 items. Hand grip strength and gait speed were measured regularly by physical examination. Linear mixed-effects models estimated the backward trajectories of frailty, grip strength and gait speed before dementia, compared to controls. Secondary analyses were stratified by sex and ApoE ε4 carrier status. RESULTS: Higher frailty burden, with a steeper increase over time, was found in the years before dementia, compared to controls (P-interaction < .001). Hand grip strength and gait speed declined more rapidly in dementia cases than in controls (P-interaction < .001 for both). Differences between cases and controls became consistently significant four to six years prior to dementia (P-contrast < .001). An earlier divergence across all three measures was observed for females, and to a lesser extent in ApoE ε4 non-carriers. DISCUSSION: Functional decline occurs within the decade before dementia onset, with gait speed being the earliest indicator. These findings support the utility of functional measures as early markers of dementia risk, with potential implications for targeted monitoring and preventative strategies.