Getting outside for some daylight could be good for more than your mood. A new study of more than 87,000 adults found that exposure to brighter light during the day was associated with a lower risk of developing dementia. The results suggest that the amount of daylight we receive may be an underappreciated factor in long-term brain health.
The study, published in the journal General Psychiatry, followed 87,577 adults who wore wrist devices that measured their exposure to light during the day and night. During a median follow-up of 8.1 years, 741 dementia cases occurred.
Researchers found that people exposed to higher levels of daytime light, averaging over 1,000 lux, were 16% less likely to develop dementia. Spending more time in even brighter conditions, at least 5,000 lux, was linked to additional reductions in risk.
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Bright daylight for less than 42 minutes may be a warning sign
One of the more surprising findings concerned people who spent very little time in bright daylight. The study found that less than 42 minutes of bright light each day was a better predictor of dementia than six established risk factors.
That might be particularly the case for people who spend most of their day indoors, whether that’s working at a desk or seldom stepping outside. However, the researchers did not specify how much time people should spend outdoors to lower their risk of dementia.
The study also didn’t find a statistically significant link between nighttime light exposure and dementia risk. “Daytime light exposure may be a new marker for dementia risk,” said corresponding author Hongliang Feng of Guangzhou Medical University in China. Thus, daytime brightness might be more important for the link researchers discovered.
But it’s worth putting the findings in perspective. The study found an association between exposure to daylight and risk of dementia, but did not prove that getting more sunlight protects against the condition. There may be other factors at play in the relationship, and more research is needed to understand what is going on.
For now, the findings are just another reason to be mindful of our daily habits and how much time we spend indoors. But more daylight should not be seen as a proven dementia prevention measure.
