An international team of researchers led by scientists from Guangzhou Medical University in China has found that insufficient bright daylight may serve as a new marker for the likelihood of developing dementia. The results of the large-scale study were published in General Psychiatry, with ScienceDaily reporting on the findings, according to infohub.kz.
The authors found that regular exposure to good daylight is associated with a 16 percent reduction in the risk of cognitive decline. The study covered more than 87,000 people and showed that a lack of daylight is more dangerous than several traditional risk factors.
The researchers analyzed objective data from 87,577 adult volunteers who continuously wore wrist trackers with accelerometers and optical sensors. The devices accurately recorded light levels during both daytime and nighttime. Over a median follow-up of 8.1 years, 741 participants were newly diagnosed with dementia.
Data analysis showed that people with average daytime light levels above 1000 lux (corresponding to the moderate brightness of an overcast day outdoors) had a 16 percent lower risk of developing the condition. Additional time spent in even brighter light of 5000 lux provided a more pronounced protective effect.
However, spending less than 42 minutes (0.7 hours) per day in bright light proved to be a critically dangerous indicator. Such a pronounced light deficiency was a stronger predictor of impending dementia than six long-recognized medical risk factors. Notably, the scientists found no statistically significant association between nighttime light levels and the incidence of the disease.
Lead author Hongliang Feng emphasized that daytime light levels serve as an important indicator of cognitive health, but the study is correlational and does not prove a direct cause-and-effect relationship. The findings require further clinical verification.