Longitudinal Relationships between Daily Activity and Hippocampal Atrophy in Japanese Dwellers

Background The relationship between physical activity and hippocampal volume is important; however, most studies have used questionnaires to measure physical activity. We aimed to determine whether maintaining high levels of daily physical activity measured by an accelerometer reduces hippocampal atrophy in community-dwelling adults. Methods This cohort study used data from community-dwelling adults aged ≥60 years who participated in the National Institute for Longevity Sciences Longitudinal Study of Aging, which is a population-based prospective cohort study of approximately 2,300 Japanese adults. Tertiles of step count, light-intensity physical activity, and moderate-to-vigorous-intensity physical activity (MVPA) were measured using accelerometers. Changes in the hippocampal and total grey matter volumes over approximately 10 years were obtained from high-resolution 3D T1-weighted Magnetic Resonance Imaging (MRI) images. Results The analysis included 287 men and 264 women, with no history of head surgery, dementia, or stroke at baseline, who completed the MRI scans and follow-up surveys. Significant interactions between MVPA and years since baseline with whole and right hippocampal volumes were observed only in men (p<.05). Annual whole hippocampal atrophy volumes in the lowest, intermediate, and highest MVPA groups were -72.11, -58.25, and -59.53 mm3, respectively. Right hippocampal atrophy volumes were -36.93, -28.47, and -28.53 mm3, respectively. The total and right hippocampal volumes in the lowest MVPA group declined more rapidly than those in the other groups. Conclusions Lower MVPA levels in men were associated with higher rates of both total and right hippocampal atrophy. The relationship between MVPA and atrophy may help develop dementia prevention strategies.