No abstract

Objectives: Physical activity (PA) has been hypothesized to spare gray matter volume in late adulthood, but longitudinal data testing an association has been lacking. Here we tested whether PA would be associated with greater gray matter volume after a 9-year follow-up, a threshold could be identified for the amount of walking necessary to spare gray matter volume, and greater gray matter volume associated with PA would be associated with a reduced risk for cognitive impairment 13 years after the PA evaluation. Methods:In 299 adults (mean age 78 years) from the Cardiovascular Health Cognition Study, we examined the association between gray matter volume, PA, and cognitive impairment. Physical activity was quantified as the number of blocks walked over 1 week. High-resolution brain scans were acquired 9 years after the PA assessment on cognitively normal adults. White matter hyperintensities, ventricular grade, and other health variables at baseline were used as covariates. Clinical adjudication for cognitive impairment occurred 13 years after baseline.

Elders who maintain cognitive function have a unique profile that differentiates them from those with minor decline. Importantly, some of these factors are modifiable and thus may be implemented in prevention programs to promote successful cognitive aging. Further, factors associated with maintenance may differ from factors associated with major cognitive decline, which may impact prevention vs treatment strategies.

Limited health literacy was prevalent and was associated with low socioeconomic status, comorbidities, and poor access to health care, suggesting that it may be an independent risk factor for health disparities in older people.

Global and executive cognitive functions predict declines in gait speed. The association of ECF with gait speed decline is attenuated by comorbid conditions, particularly depression. Elucidation of the mechanisms underlying these associations may point to new pathways for the treatment of physical decline associated with diminished cognitive function.

In older adults, gait speed predicts 3 year incidence of bathing or dressing dependence, mobility difficulty, and a composite outcome of disability and mortality.

Performance measures of physical function (gait speed, chair stands, standing balance) and cognitive function [Teng-modified Mini-Mental Status Exam (3MS) and digit symbol substitution test (DSST)] were assessed at baseline in 3,075 participants in the Health, Aging and Body Composition Study. Each physical function measure was examined for the strength and magnitude of association with cognitive function. All physical function measures were associated with both the 3MS and DSST scores (p < 0.001), and in multivariate analysis each relationship was independent of demographic characteristics, weight, physical activity and comorbid health conditions of participants. The association of motor performance was consistently greater for the DSST than the 3MS and, among the motor tests, gait speed retained a significant association with both cognitive measures independent of demographic, weight, physical activity and comorbid health conditions. In this large cohort of high-functioning older adults, the correlation between physical and cognitive function was not entirely explained by demographics. Longitudinal studies are needed to determine the direction of causality in this relationship.

In this well-functioning cohort, several cognitive tasks were associated with gait speed cross-sectionally and predicted longitudinal gait speed decline. These data are consistent with a shared pathology underlying cognitive and motor declines but do not suggest that specific executive cognitive deficits account for slowing of usual gait in aging.