Abstract
Maintaining high levels of daily activity and physical capability have been proposed as important constituents to promote healthy brain and cognitive aging. Studies investigating the associations between brain health and physical activity in late life have, however, mainly been based on self-reported data or measures designed for clinical populations. In the current study, we examined cross-sectional associations between physical activity, recorded by an ankle-positioned accelerometer for seven days, physical capability (grip strength, postural control, and walking speed), and neuroimaging based surrogate markers of brain health in 122 healthy older adults aged 65–88 years. We used a multimodal brain imaging approach offering complementary structural MRI based indicators of brain health: global white matter fractional anisotropy (FA) and mean diffusivity (MD) based on diffusion tensor imaging, and subcortical and global brain age based on brain morphology inferred from T1-weighted MRI data. In addition, based on the results from the main analysis, follow-up regression analysis was performed to test for association between the volume of key subcortical regions of interest (hippocampus, caudate, thalamus and cerebellum) and daily steps, and a follow-up voxelwise analysis to test for associations between walking speed and FA across the white matter Tract-Based Spatial Statistics (TBSS) skeleton. The analyses revealed a significant association between global FA and walking speed, indicating higher white matter integrity in people with higher pace. Voxelwise analysis supported widespread significant associations. We also found a significant interaction between sex and subcortical brain age on number of daily steps, indicating younger-appearing brains in more physically active women, with no significant associations among men. These results provide insight into the intricate associations between different measures of brain and physical health in old age, and corroborate established public health advice promoting physical activity.
Highlights
Magnetic resonance imaging (MRI) studies have revealed substantial age-related changes in the human brain, including cortical and subcortical atrophy, ventricular enlargement, and white matter alter ations (Fjell et al, 2009; Garde et al, 2000; Westlye et al, 2010; Ylikoski et al, 1995)
The main purpose of the current study was to examine the associa tion between objective measures of physical activity level and capa bility, and two complementary structural MRI based indicators of brain health: white matter fractional anisotropy (FA) and mean diffusivity (MD) based on Diffusion tensor imaging (DTI) and brain age gap (BAG) based on brain morphology
We have demonstrated that different markers of brain white matter structure and brain aging are associated with objectively measured daily activity and physical capability
Summary
Magnetic resonance imaging (MRI) studies have revealed substantial age-related changes in the human brain, including cortical and subcortical atrophy, ventricular enlargement, and white matter alter ations (Fjell et al, 2009; Garde et al, 2000; Westlye et al, 2010; Ylikoski et al, 1995). As further understanding of the complexity and biological basis of brain and cognitive aging evolves, more targeted preventive measures and innovative models of geriatric care is expected to be developed as part of public health programs. Physical health indicators, such as daily activity level, balance, walking speed, and hand-grip strength, are associated with healthy aging (Kuh, 2007; Vermeulen et al, 2011), and represent a putative malleable moderator of brain aging. Higher number of accelerometer-measured daily walking steps was related to larger surface area in subregions of the hippocampus in women but not in men (Varma et al, 2016)
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