Does biological sex moderate the association of nature exposure with brain volume? A cross‐sectional analysis of the UK Biobank

Abstract

AbstractBackgroundNeighbourhood nature spaces are associated with brain health. Biological sex moderates the associations of various lifestyle and environmental factors with brain health, but it is unclear whether sex moderates associations between nature exposure and brain structure. We thus investigated whether sex moderates the association of residential nature exposure with brain structure in the UK Biobank cohort.MethodsWe conducted a cross‐sectional analysis of the UK Biobank study. We included cognitively healthy participants with available nature exposure data at study entry (2006‐2010) who completed a 3T structural brain MRI (2014‐2021; N = 37,880). Residential nature exposure was estimated as the percentage of land classified as natural environment within 1000m of a participant’s home. We indexed total grey matter volume and total white matter volume, normalized for head size, and hippocampal volume averaged from both hemispheres. We performed linear regressions to assess the independent associations of residential nature exposure and biological sex with brain structure. We then assessed whether sex moderated the association between residential nature exposure and brain structure, and plotted simple slopes to interpret interaction effects. All models adjusted for age, body mass index (kg/m2), educational attainment, income, physical activity (min/day), time spent outdoors (hours/day), smoking status, disability status, Townsend deprivation index, and population density.ResultsAt study entry, mean age was 55 years (SD = 7.53 years) and 53% of participants were female. Average residential nature exposure was 44% (SD = 26%). Every 10% increment in residential nature exposure was associated with 737 mm3 greater grey matter volume (p<0.0001) and 601 mm3 greater white matter volume (p<0.0001). Females had 24,270 mm3 greater grey matter volume (p<0.0001), 9,703 mm3 less white matter volume (p<0.0001), and 223 mm3 less hippocampal volume than males (p<0.0001). Sex moderated the association of residential nature exposure with total grey matter volume, such that every 10% increment in nature exposure attenuated sex differences in grey matter volume by 422 mm3 (p = 0.020) (Figure 1).ConclusionThese results suggest that neighbourhood nature spaces may benefit brain health, and that males may be more sensitive than females to these potential benefits. Longitudinal analyses are needed to verify these findings.