Abstract
INTRODUCTION: Examining motor and cognitive decline in separate models may underestimate their associations. METHODS: In a single trivariate model, we examined the levels and rates of decline of three phenotypes, sensor-derived total daily physical activity, motor abilities, and cognition in 1007 older adults during 6 years of follow-up. In 477 decedents, we repeated the model adding fixed terms for indices of nine brain pathologies. RESULTS: Simultaneous rates of decline of all three phenotypes showed the strongest correlations with shared variance of up to 50%. Brain pathologies explained about 3% of the variance of declining daily physical activity, 9% of declining motor abilities, and 42% of cognitive decline. DISCUSSION: The rates of declining cognitive and motor phenotypes are strongly correlated and measures of brain pathologies account for only a small minority of their decline. Further work is needed to elucidate the biology underlying correlated cognitive and motor decline in aging adults.