Daytime Light Exposure Linked to Lower Dementia Risk

Higher daytime light exposure was associated with a significantly lower risk of developing dementia, while nighttime light exposure showed no significant relationship. In this study of 87,577 dementia-free UK adults (average age 62 years) followed for a median of 8.1 years, 741 participants developed dementia. Researchers measured light exposure using wrist-worn devices over seven days and found that exposure to daytime light levels above 1,000 lux was associated with a 16% lower risk of dementia. Spending at least 0.7 hours per day in bright light (≥5,000 lux) was linked to an even greater risk reduction of about 17%. Exploratory analyses suggested that healthier circadian rest–activity rhythms and favorable brain structural changes may explain up to one-third of this protective association. The benefits of daytime light exposure were particularly strong among high risk individuals with high nighttime light exposure, an evening chronotype (night owl), or the APOE ε4 genetic risk variant, with dementia risk reductions reaching as much as 41%. Notably, insufficient bright daytime light exposure (<0.7 hours/day) predicted dementia risk more strongly than several established risk factors, including obesity, alcohol consumption, and traumatic brain injury. These findings suggest that increasing exposure to natural daylight may represent a simple, low-cost strategy for supporting long-term brain health and reducing dementia risk. Source: https://onlinelibrary.wiley.com/