Physical inactivity is associated with Parkinson's disease mild cognitive impairment and dementia

Parkinson's disease (PD) is a neurodegenerative disorder marked by both motor symptoms and cognitive impairment. Individuals with PD are generally less physically active relative to healthy older adults. This study examined if physical activity predicted future PD mild cognitive impairment (PD-MCI) and PD dementia (PDD).Participants were part of the Parkinson's Progression Markers Initiative (PPMI), a longitudinal cohort study of individuals newly diagnosed with PD. 307 participants were followed for up to three years. Individuals were classified as cognitively normal (CN), PD mild cognitive impairment (PD-MCI), or PD dementia (PDD) at each year. A self-report measure of physical activity was completed annually. Ordinal multilevel models were computed to examine the longitudinal relationship between physical activity and cognitive status. Less self-reported engagement in physical activities predicted worse cognitive status. Specifically, we found evidence of a significant within-person effect. Individuals with PD who became less active were at greater risk of developing PD-MCI or PDD. This effect was driven by longitudinal decreases in leisure/recreational physical activities. Findings support the hypothesis that longitudinal changes in physical activity are associated with clinically meaningful diagnostic outcomes of cognitive status. Since individuals with PD are prone to sedentary behaviors, future studies are needed to determine the clinical utility of interventions promoting routine physical activity.