"To investigate the connection, researchers analyzed data from 87,577 adults who wore wrist devices equipped with accelerometers. The devices allowed scientists to measure participants' exposure to light during both the day and night. Over a median follow-up period of 8.1 years, 741 participants developed dementia.

The results revealed a notable pattern. People exposed to average daytime light levels exceeding 1,000 lux (a moderately bright light level equivalent to an overcast day outdoors) had a 16% lower risk of developing dementia. Spending longer periods in even brighter daytime light (at least 5,000 lux) was associated with further reductions in risk."
https://www.sciencedaily.com/releases/2026/10/261028232707.htm