Association of objectively measured physical activity with brain structure: UK Biobank study.

<bold>Background: </bold>Physical activity may be beneficial for cognition but mechanisms are unclear. We examined the association between objectively assessed physical activity and brain volume, with a focus on the hippocampus region.<bold>Methods: </bold>We used data from UK Biobank (n = 5272; aged 55.4 ± 7.5 years; 45.6% men) collected through 2013-2016. Participants wore the Axivity AX3 wrist-worn triaxial accelerometer for 7 days to assess habitual physical activity. Structural magnetic resonance imaging was performed using a standard Siemens Skyra 3T running VD13A SP4 to obtain images of the brain.<bold>Results: </bold>There was an association between physical activity (per SD increase) and grey matter volume after adjustment for a range of covariates, although this association was only detected in older adults (>60 years old). We also observed associations of physical activity with both left (B = 0.52, 95% CI, 0.01, 1.03; P = 0.046) and right hippocampal volume (B = 0.59, 95% CI, 0.08, 1.10; P = 0.024) in covariate-adjusted models.<bold>Conclusion: </bold>In summary, physical activity may play a role in the prevention of neurodegenerative diseases. [ABSTRACT FROM AUTHOR]