A new study published in the journal General Psychiatry has identified a potential link between daytime light exposure and the risk of developing dementia. According to the findings, greater exposure to natural daylight is associated with a lower likelihood of developing this neurodegenerative condition.

The study included 87,577 participants who wore wrist-mounted accelerometers capable of recording ambient light levels throughout the day. Over a median follow-up period of 8.1 years, 741 participants were diagnosed with dementia.

The analysis revealed that an average daytime light exposure exceeding 1,000 lux — roughly equivalent to a bright overcast day outdoors — was associated with about a 16% reduction in dementia risk. Spending longer periods in bright daylight conditions (5,000 lux or more) was linked to an even stronger protective effect.

Researchers also found that spending less than 0.7 hours per day in bright daylight was a stronger predictor of dementia risk than six traditionally recognized risk factors for the disease. In contrast, nighttime light exposure showed no significant association with dementia development.

According to study co-author Hongliang Feng of Guangzhou Medical University, daytime light exposure may represent a new potential marker for the risk of cognitive decline and dementia.

The biological mechanisms behind this association are not yet fully understood. However, scientists suggest that daylight may influence circadian rhythms, sleep regulation, metabolic processes, and inflammatory responses — all of which have previously been linked to cognitive health.

While the findings do not prove that increased daylight exposure directly prevents dementia, they add to growing evidence that everyday environmental factors may play an important role in maintaining brain health as people age.