Objectively measured physical activity, brain atrophy, and white matter lesions in older adults with mild cognitive impairment

• More physical activity was associated with significantly less brain atrophy.
• Low levels of physical activity were associated with severe white matter lesions.
• Age, sex, and mobility affected the association between activity and brain atrophy.

Physical activity may help to prevent or delay brain atrophy. Numerous studies have shown associations between physical activity and age-related changes in the brain. However, most of these studies involved self-reported physical activity, not objectively measured physical activity. Therefore, the aim of this study was to examine the association between objectively measured physical activity, as determined using accelerometers, and brain magnetic resonance imaging (MRI) measures in older adults with mild cognitive impairment (MCI). We analyzed 323 older subjects with MCI (mean age 71.4 years) who were recruited from the participants of the Obu Study of Health Promotion for the Elderly. We recorded demographic data and measured physical activity using a tri-axial accelerometer. Physical activity was classified as light-intensity physical activity (LPA) or moderate-to-vigorous physical activity (MVPA). Brain atrophy and the severity of white matter lesions (WML) were determined by MRI. Low levels of LPA and MVPA were associated with severe WML. Subjects with severe WML were older, had lower mobility, and had greater brain atrophy than subjects with mild WML (all P < 0.05). Multivariate analysis revealed that more MVPA was associated with less brain atrophy, even after adjustment for WML (β = − 0.126, P = 0.015), but LPA was not (β = − 0.102, P = 0.136). Our study revealed that objectively measured physical activity, especially MVPA, was associated with brain atrophy in MCI subjects, even after adjusting for WML. These findings support the hypothesis that physical activity plays a crucial role in maintaining brain health.