Less than 42 minutes of daylight daily may raise dementia risk, study finds
Exposure to less than 42 minutes of bright daylight per day may increase dementia risk, while higher light levels are linked to a 16% lower risk, researchers say.
Key Takeaways
AIA recent study published in the journal General Psychiatry and reported by Science Daily has found that exposure to bright daylight is linked to a reduced risk of developing dementia.
The study involved 87,577 adults who wore wrist devices equipped with accelerometers to measure their exposure to light during the day and night. Participants were followed for a median of 8.1 years, during which 741 cases of dementia were diagnosed.
Researchers found that people exposed to daylight levels above 1,000 lux—roughly equivalent to the light on a cloudy day outdoors—were 16% less likely to develop dementia compared to others.
Spending longer periods in even brighter light, at 5,000 lux or more, was associated with an even greater reduction in risk.
The results indicated that very limited exposure to bright daylight—less than 0.7 hours per day (under 42 minutes)—was a strong predictor of dementia risk, surpassing six other known risk factors in its predictive power.
By contrast, the researchers found no statistically significant link between nighttime light exposure and dementia risk, highlighting daylight as the most relevant factor in this relationship.
Hongliang Feng, the lead researcher from Guangzhou Medical University in China, said that daylight exposure could serve as a new indicator for dementia risk, potentially allowing it to be used in future brain health assessments.
However, the researchers emphasized that the study does not prove a direct causal relationship, but rather points to a strong association that requires further research to understand the underlying biological mechanisms.
The researchers suggested that daylight may help regulate the body’s circadian rhythm, improve sleep quality, and support neurological processes linked to brain health.
Still, additional studies are needed to determine whether increasing natural light exposure could be an effective intervention to reduce dementia risk.
The findings highlight the importance of a simple daily factor that is often overlooked, but which may provide a key indicator of brain health and the risk of cognitive decline with age.