A large study suggests that daytime bright-light exposure may be associated with a lower 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 16% lower risk of dementia over a median follow-up of 8.1 years. However, the findings show an association rather than proving that sunlight directly prevents dementia.
Daytime light exposure and 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 daytime and nighttime hours. During the study period, 741 participants developed dementia.
The results, reported in General Psychiatry, indicated that people exposed to average daytime light levels above 1,000 lux had a 16% lower risk of developing dementia. This level is comparable to the moderately bright light found outdoors on a cloudy day.
Spending more time in even brighter daylight—at least 5,000 lux—was associated with a further reduction in risk.
Very low daytime light exposure 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 daytime bright light each 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 exposure to light at night, 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 that increasing sunlight exposure directly prevents dementia. Instead, they identify daytime light exposure as a potentially useful indicator of dementia risk and a factor that warrants further investigation.
Source: www.sciencedaily.com