A large study suggests that the amount of bright daylight people receive may be associated with their risk of developing dementia. Among 87,577 adults monitored with wrist-worn devices, those exposed to more than 1,000 lux of light during the day had a lower risk of dementia over a median follow-up of 8.1 years. The findings point to daytime light exposure as a potentially overlooked indicator of brain health, although they do not prove that sunlight directly prevents dementia.
Bright daylight was associated with lower dementia risk
Researchers analyzed data from 87,577 adults who wore wrist devices equipped with accelerometers. The devices measured participants’ exposure to light during both the day and night. During the study period, 741 participants developed dementia.
People exposed to average daytime light levels above 1,000 lux had a 16% lower risk of developing dementia. That level of illumination is moderately bright and is comparable to the light outdoors on a cloudy day. Spending more time in brighter daylight—at least 5,000 lux—was associated with a further reduction in risk.
Very little daytime light was a notable risk indicator
One of the most striking findings involved participants who received very little bright light during the day. Getting less than 0.7 hours, or 42 minutes, of bright daytime light per day was a stronger predictor of dementia than six established dementia risk factors.
The researchers found no statistically significant association between nighttime light exposure and dementia risk. This suggests that daytime brightness, rather than nighttime light exposure, may be particularly relevant to the relationship identified in the study.
“Daytime light exposure may serve as a new indicator of dementia risk,” said corresponding author Hongliang Feng, Ph.D., from Guangzhou Medical University in China.
The findings do not establish cause and effect
The results, reported in General Psychiatry, show an association but do not prove that getting more sunlight directly prevents dementia. Instead, they identify daytime light exposure as a potentially useful indicator of dementia risk and a factor that merits further investigation.
Source: www.sciencedaily.com
