BACKGROUND: Gait speed (GS) and psychomotor speed (PS) could be considered as two different dimensions of age-related slowness and both measures are associated with higher risk of adverse health-related outcomes among elderly people.

OBJECTIVE: To determine the association between GS, PS, and incident dementia among community-dwelling older adults.

METHODS: Twelve-year longitudinal study of 1,265 participants in the Bordeaux Three-City Study, a French prospective cohort designed to determine the risk of dementia and cognitive impairment attributable to cardiovascular risk factors. Participants completed a battery of cognitive tests, including time to complete the Trail Making Test A, and a walking speed test. The incidence of dementia was determined over the 12-year follow-up period. Cox proportional hazards models with delayed entry were used to estimate the cumulative risk of dementia and were adjusted for sex, education, and ApoE4 genotype.

RESULTS: Mean age of participants was 74.0 years (SD 4.8). Over the 12-year follow-up, 203 participants developed dementia. GS and PS were both independent predictors of incident all-cause dementia after 12 years of follow-up. For a one SD increase of either GS or PS, the hazard ratio (HR) for Alzheimer's disease was 1.2 (95% CI = 1.02-1.32) and 1.4 (95% CI = 1.2-1.61), respectively; whereas for incident vascular dementia, the HR was 1.3 (95% CI = 1.05-1.71) and 1.5 (95% CI = 1.16-2.08), respectively. No significant interaction between GS and PS was observed.

CONCLUSIONS: In older French people aged 65+, our findings showed that both low GS and PS were independently associated with risk of incident Alzheimer's disease and vascular dementia.