Abstract
Background:
Leisure time physical activity (LTPA) has been associated with a lower risk of dementia, but whether the effects are specific to particular cognitive abilities or improvement in functional status remains unclear. We examined LTPA in relation to domain-specific neurocognitive (NC) performance and change over time in a diverse community sample.
Methods:
Data on LTPA was collected during enrollment (1993-2001) into the Northern Manhattan Study (NOMAS), a prospective cohort study of risk factors for stroke and cognitive decline, using a validated in-person questionnaire, and two waves of NC assessments were done on a subcohort of participants undergoing brain MRI an mean of six and 12 years later (NC1: 2003-2008; NC2: 2008-2014). Baseline LTPA was defined in two manners: (1) maximum intensity of all activities performed categorized as moderate-heavy, light, and none; (2) total summarized as a continuous variable with the metabolic equivalent (MET) score, a composite of total reported intensity and time. Factor analysis-derived construct-relevant cognitive domains, including memory (MEM), executive function (EXEC), processing speed (PS), and language ability (LA), were computed by averaging z-transformed NC test scores. We used multivariable linear regression to examine LTPA in relation to baseline domain-specific NC performance, and change in performance over time, adjusting for socio-demographics, vascular risk factors, and MRI markers of cerebrovascular injury (white matter hyperintensity volume and total cerebral volume, both adjusted for total intracranial volume, and silent brain infarcts).
Results:
There were 1236 participants (mean age=64 years, 61% women, 67% Latino, 18% black, 15% white) with LTPA and NC data, and 879 with a second NC assessment. Moderate-to-heavy activity was associated with higher baseline LA (p <0.05) and PS (p <0.05), and with a protective effect on change of MEM (p <0.05) and PS (p <0.05); these effects were not attenuated after adjustment for MRI variables. Total MET-score was not associated with baseline NC domain performance. However, participants with greater MET-scores had significantly less decline in processing speed adjusting for age and education. Inclusion of vascular risk factors and MRI markers each attenuated these associations though they remained statistically significant.
Conclusions:
Leisure time physical activity is independently protective against a decline in processing speed and memory, and was partly mediated by MRI markers. Leisure-time physical activity may protect against dementia through preventing cerebrovascular correlates of brain injury.