Trajectories of cognitive and motor function between ages 45 and 90 years: a population-based study.

BACKGROUND To establish trajectories of cognitive and motor function, and to determine the sequence of change across individual tests in community-dwelling individuals aged 45-90 years. METHODS Between 1997-2016, we repeatedly assessed cognitive function with five tests in 9,514 participants aged 45-90 years from the population-based Rotterdam Study. Between 1999-2016, we measured motor function with three tests in 8,297 participants. All participants were free from dementia, stroke, and parkinsonism. We assessed overall and education-specific cognitive and motor trajectories using linear mixed models with age as time scale. Next, we determined the sequence of change across individual tests. RESULTS The number of assessments per participant ranged between 1-6 (mean interval, years[SD]: 5.1[1.4]) for cognitive function, and 1-4 (5.4[1.4]) for motor function. Cognitive and motor trajectories declined linearly between ages 45-65 years, followed by steeper declines after ages 65-70 years. Lower educated participants had lower cognitive function at age 45 years (baseline), and declined faster on most cognitive, but not on motor tests than higher educated participants. Up to a 25-year age difference between the fastest and slowest declining test scores was observed. CONCLUSIONS On a population-level, cognitive and motor function decline similarly. Compared to higher educated individuals, lower educated individuals had lower cognitive function at baseline, and a faster rate of decline thereafter. These educational-effects were not seen for motor function. These findings benefit the understanding of the natural course of cognitive and motor function during aging, and highlight the role of education in the preservation of cognitive but not motor function.