Brighter days, healthier brains: people who caught more daylight were less likely to develop dementia

A wrist sensor, worn for a week, turned out to say something striking about the brain years later. Researchers followed 87,577 adults for a median of just over eight years, measuring the light they actually lived in rather than asking them to remember it. People whose average daytime light topped 1,000 lux — roughly the brightness of an overcast day outdoors — were 16% less likely to develop dementia, and those who got at least 42 minutes a day of brighter light, at 5,000 lux or more, were 17% less likely. Getting less than 42 minutes of bright daylight predicted dementia more strongly than six well-known risk factors, including obesity and heavy drinking, while light at night showed no link at all. The study, in the journal General Psychiatry, shows a link, not proof that daylight prevents dementia — but as lead author Hongliang Feng of Guangzhou Medical University puts it, daytime light may be a new marker doctors can watch.

SDG 3 · Good health and well-being