Background: How the environment in which physical activity takes place influences brain health remains insufficiently studied. We aimed to investigate the association between outdoor physical activity and dementia in older adults, and to examine whether residential green space (GS) modifies this association.
Methods: This prospective longitudinal study used UK Biobank data from 187,724 adults aged 60-73 years at baseline (2006-2010) and 36,854 with brain Magnetic Resonance Imaging (2014-2021). Outdoor activity (via Metabolic Equivalent of Task) and GS (within 300 m of homes) were assessed, with dementia incidence tracked through electronic records until December 2022. Neuroimaging markers included hippocampal and total gray-matter volumes, and white-matter hyperintensity volume. Cox proportional hazards and linear regression models were applied.
Results: During a mean follow-up of 13.01 years, 7218 participants (47.1% female) developed dementia. After adjusting for covariates, higher outdoor activity is associated with a lower risk of all-cause dementia (HRtop vs bottom quartile = 0.84, 95% Confidence Interval [CI] 0.78-0.90). This association is most pronounced for vascular dementia (HR:0.72, 95%CI 0.63-0.83) and is stronger among those living in areas with high, compared to low, residential GS (0.73, 95%CI 0.63-0.85 vs 0.86, 95%CI 0.79-0.93, pinteraction = 0.04). Higher outdoor activity is also associated with higher hippocampal and total gray-matter volumes and fewer white-matter hyperintensities. A combined effect of outdoor activity and GS on hippocampal volume is observed.
Conclusions: Outdoor activity is linked to lower dementia risk, particularly in those living in more accessible GS. These findings underscore the importance of urban planning that prioritizes accessible GS to promote brain health in the aging population.
Spending time outdoors and being active, especially in natural environments, is known to benefit mental health. Some studies suggest that access to green spaces may also help protect against dementia, but long-term effects and possible brain-related explanations are not well understood. In this study, we followed over 180,000 older adults for 13 years and found that those engaging in more outdoor physical activity had a lower risk of developing dementia. This protective effect was stronger for people living in neighbourhoods with more accessible green spaces. Outdoor activity was also linked to better brain structure. These findings suggest that increasing outdoor activities for older adults—especially in green areas—could help support brain health as they age.
© 2025. The Author(s).