Cognitive and motor abilities are generally considered unique and separate functional outputs of neural systems. However, to some extent they rely on similar underlying neural processes. For example, motor function, especially skilled movements such as those required to produce language and complex movements, require motor programs which can be impaired and lead to loss of learned motor abilities despite intact strength and coordination. A unique feature of the Memory and Aging Project is the detailed longitudinal data on both cognitive and motor function. The latter includes measures of parkinsonian signs, an overall measure of motor function based on strength and performance measures, a measure of physical frailty that includes measures of muscle structure and function as well as walking speed, all of which were related to cognitive outcomes. Other studies have also shown both cross-sectional and longitudinal associations between cognitive and motor function [184–194]. In addition, several risk factors, including APOE, social activity, loneliness, neuroticism, respiratory function, renal function and diabetes were related to both cognitive and motor abilities in either cross-sectional or longitudinal analyses, consistent with some prior studies [195]. Together, these findings provide strong evidence of common causation of decline in cognitive and motor abilities.
