Daytime average light exposure above 1,000 lux -- equivalent to an overcast day outdoors -- was tied to reduced dementia risk.Exposure to bright daytime light for at least 42 minutes/day also was linked with lower incident dementia.Circadian regulation may partly explain the relationship, exploratory analyses suggested.
People exposed to higher levels of daytime light had a lower risk of dementia, prospective data from 88,000 U.K. Biobank participants showed.
Over 8 years of follow-up, people who had an average daytime light exposure above 1,000 lux -- a moderately bright level of light, equivalent to an overcast day outdoors -- had a 16% reduced dementia risk (HR 0.84, 95% CI 0.71-0.99, P=0.039), reported Hongliang Feng, MD, PhD, of Guangzhou Medical University in China, and co-authors.
Exposure to bright daytime light of at least 5,000 lux for at least 0.70 hr/day (42 minutes) also was tied to lower dementia risk (HR 0.83, 95% CI 0.70-0.99, P=0.036), Feng and colleagues reported in General Psychiatry.
"This exposure metric outperformed six traditional dementia risk factors, including obesity, alcohol intake, and traumatic brain injury, in predictive strength," Feng said. "The protective effect was most pronounced in high-risk groups -- evening chronotypes, people with high nighttime light exposure, and APOE4 carriers -- with risk reduction reaching up to 41%," he told MedPage Today.
