Associations between natural sunlight exposure and brain structural markers: a prospective study in the UK Biobank

ObjectiveSunlight is closely intertwined with daily life. It remains unclear whether there are associations between sunlight exposure and brain structural markers. MethodsThis longitudinal study utilized baseline data (2006-2010) and follow-up data (2014+) from the UK Biobank. General linear regression analysis was employed to compare the differences in brain structural markers among different sunlight exposure time groups. Stratification analyses were performed based on sex, age, and diseases (hypertension, stroke, diabetes). Limiting cubic splines were performed to examine the dose-response relationship between natural sunlight exposure and brain structural markers, with further stratification by season. To control environmental and genetic factor, we adjusted PM2.5 and PRS for Alzheimers disease. ResultsA total of 27,474 participants were included in the final analyses. The association of sunlight exposure time with brain structural markers was found in the upper quartile compared to the lower quartile. Prolonged natural sunlight exposure was associated with the volumes of total brain ({beta}: -0.051, P < 0.001), white matter ({beta}: -0.031, P = 0.023), gray matter ({beta}: -0.067, P < 0.001), and white matter hyperintensities ({beta}: 0.059, P < 0.001). These associations were more pronounced in males and individuals under the age of 60. With daily sunlight exposure approximately exceeding 2 hours, we observed that total brain volume and gray matter volume decreased, while white matter high hyperintensity volume increased with prolonged sunlight exposure duration. ConclusionsThis study demonstrates that prolonged exposure to natural sunlight is associated with brain structural markers change. These findings offer new insights into the mechanisms underlying the association between natural sunlight and brain health.