Adults who received more bright daylight had a lower risk of developing dementia, according to a new study.
Getting less than 42 minutes of bright daylight per day was a stronger predictor of dementia than six established risk factors.
Researchers say the findings highlight a possible connection between daylight exposure and brain health, but more research is needed to determine whether sunlight can actually help prevent dementia.
Getting outside for some fresh air and sunshine can be an easy way to break up the day. But new research suggests that spending time in bright daylight could have another potential benefit: supporting long-term brain health.
A study published in General Psychiatry found that people who received more daylight exposure had a lower risk of developing dementia over time. In particular, researchers identified a connection between spending at least 42 minutes in bright daylight each day and a reduced risk of the condition.
The findings offer a new perspective on how everyday environmental factors may relate to dementia risk. However, researchers caution that the study found an association, not proof that getting more sunlight directly prevents dementia.
How researchers studied daylight exposure and dementia
To investigate the potential connection, researchers examined health and activity data from 87,577 adults enrolled in the U.K. Biobank who did not have dementia when the study began. Participants had an average age of about 62, and nearly 57% were women.
Rather than asking people to estimate how much time they spent outside, researchers used wrist-worn devices to measure participants' exposure to light. Participants wore the devices for seven days, allowing researchers to track both daytime and nighttime light levels.
The team then followed participants for a median of 8.1 years, using primary care records, hospital admissions, and death records to identify new dementia diagnoses.
During that period, 741 participants developed dementia. Researchers analyzed the data to see whether differences in light exposure were associated with the likelihood of developing the condition. They also explored whether sleep-wake patterns and brain structures might help explain the relationship.
What the findings could mean for consumers
The results revealed a notable relationship between daytime light and dementia risk. Participants exposed to average daytime light levels above 1,000 lux had a 16% lower risk of developing dementia than those with lower exposure.
The researchers also found that spending more time in brighter light was associated with additional reductions in risk. Specifically, exposure to at least 5,000 lux for 42 minutes or longer each day was linked to a lower dementia risk.
In fact, receiving less than 42 minutes of this bright daylight was a stronger predictor of dementia than six established risk factors, including obesity, alcohol consumption, and traumatic brain injury. Interestingly, nighttime light exposure was not significantly associated with dementia risk.
For consumers, the findings offer another reason to pay attention to daily daylight exposure. Getting outside during the day may be a simple habit worth exploring, but the research does not establish a specific amount of sunlight that people should get to prevent dementia.
The researchers say additional studies are needed to better understand the relationship and determine whether increasing daytime light exposure could eventually become part of dementia prevention strategies.