Bright Daylight and Brain Health: Researchers Identify 42-Minute Threshold Linked to Dementia Risk - Video

Greater exposure to bright daylight may be associated with a lower risk of developing dementia, according to a new study. Researchers found that adults who experienced higher levels of daytime light were less likely to develop dementia, suggesting that daily light exposure could be an important factor in understanding brain health.

Published in the journal General Psychiatry, the study investigated the relationship between daytime and nighttime light exposure and the risk of dementia among adults.

Researchers analysed data from 87,577 participants who wore wrist-mounted devices equipped with sensors to measure their exposure to light throughout the day and night.

The participants were followed for a median period of 8.1 years, during which 741 individuals developed dementia.

The findings revealed that participants exposed to average daytime light levels exceeding 1,000 lux had a 16% lower risk of developing dementia.

Lux is a unit used to measure light intensity, with 1,000 lux representing a level of brightness comparable to an overcast day outdoors.

Importantly, spending longer periods in brighter daytime light, measuring at least 5,000 lux, was associated with further reductions in dementia risk.

Researchers also found that individuals who received less than 42 minutes of bright daylight daily had a particularly elevated risk.

Interestingly, this limited daytime light exposure was a stronger predictor of dementia than six established risk factors examined in the study.

However, nighttime light exposure showed no statistically significant association with dementia risk.

Researchers suggested that daytime light exposure may serve as a useful indicator for identifying individuals at increased risk of cognitive decline.

Nevertheless, the observational study could not establish that greater sunlight exposure directly prevents dementia.

The findings highlight the potential importance of daytime light exposure in brain health and suggest that further research is needed to determine whether increasing daily light exposure could help reduce dementia risk.

REFERENCE: Nana Zheng, et al.; Associations between wearable‐device‐measured daytime and nighttime light exposures and dementia risk: A prospective cohort study. General Psychiatry, 2026; 39 (3) DOI: 10.1002/gps3.70039