Spending time in bright light could help support brain health, according to a study of nearly 88,000 older adults that found a connection between daily light exposure and lower dementia risk.
Participants receiving bright light for 42 minutes or more each day had a dementia risk 17% lower in relative terms.
Here's what to know
A team led by researchers at Guangzhou Medical University in China analyzed UK Biobank data from participants who recorded light levels with sensors worn around the clock for a week, ScienceAlert reported. The team then tracked dementia diagnoses over roughly eight years.
Dementia risk was lower among people who spent more time in natural or artificial light each day, the researchers reported in General Psychiatry. The 42-minute finding involved bright light measuring at least 5,000 lux.
Among night owls, ScienceAlert reported that more daytime light corresponded to a reduction in dementia risk of as much as 41%. For participants carrying the APOE ε4 allele, a genetic risk factor for dementia, the association reached up to 27%.
The connection was also particularly evident among people exposed to higher levels of light at night.
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More background
According to ScienceAlert, light reaching the eyes triggers the brain's "master clock," which coordinates rhythms involved in waking and sleeping. The body's daily schedule therefore depends in part on light.
Sleep disorders or disrupted sleep-wake cycles are a frequent part of life for people with dementia.
Participants with greater daytime light exposure also tended to have greater brain tissue volume or surface area in the medial temporal lobe, a region involved in memory that dementia often affects early.
Other possible explanations involve mood and vitamin D. According to ScienceAlert, previous studies have associated daytime brightness with a reduced likelihood of major depressive disorder, itself a dementia risk factor.
Dementia risk is also linked to vitamin D, which the body produces when sunlight reaches the skin.
What can be done?
People at higher risk of cognitive decline were a particular focus of the researchers' recommendation: Brighter daytime surroundings could offer a low-cost way to support brain health.
However, typical indoor lighting may fall well short of the brightness levels examined in the study. According to the authors, nearly 90% of a modern person's day is spent inside, with daytime artificial lighting usually supplying roughly 300 to 500 lux.
The team identified daytime exposure of at least 1,000 lux as a potentially useful target for further prevention efforts. Both sunlight and artificial light count toward this target.
"These findings position daytime light exposure as a novel, robust and measurable indicator of dementia risk," the study authors wrote. "They could inform future research into light-based interventions and public health guidelines that recommend increased daytime light exposure as a low-cost strategy to support brain health, particularly in high-risk populations."
Where can I learn more?
Light exposure is one of many everyday factors researchers are studying in relation to brain health and aging.
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