For a while now, Dr. Wiggy has written that getting adequate vitamin D is associated with good health.

But generally, when he’s talked about vitamin D, he’s focused on bone health or immune system function.

And while we can obviously get vitamin D from sunlight, and that’s good for us, something else may be at play besides vitamin D levels alone…the sun’s brightness could positively affect us.

The sad part is that in this modern age, most people spend a lot of time indoors. And even a brightly lit home or office is usually much dimmer than being outside during the day.

That difference may matter more than researchers once thought.

How Brighter Days Were Linked to Lower Dementia Risk

A large study of nearly 88,000 adults found that people exposed to brighter daytime light had a lower risk of developing dementia in the years that followed.

The finding does not prove that daylight prevents dementia, but it adds another interesting piece to what scientists are learning about light, sleep, circadian rhythms, and brain health.

Researchers analyzed data from 87,577 adults who wore wrist devices that measured light exposure for seven days.

Researchers then followed participants for a median of just over eight years.

During that time, 741 developed dementia.

People whose average daytime light exposure exceeded 1,000 lux had about a 16% lower risk of dementia compared with those exposed to dimmer daytime conditions.

Lux measures brightness.

Typical indoor lighting is often only a few hundred lux. Even an overcast day outdoors can easily reach around 1,000 lux or more.

Researchers also found that people who spent at least 42 minutes a day in very bright light (5,000 lux or higher) had about a 17% lower dementia risk than those who spent less time at that level.

That amount of light is much easier to get outside than sitting near an indoor lamp.

Interestingly, nighttime light exposure was not significantly associated with dementia risk in the overall analysis.

Wondering Why Would Daylight Affect the Brain?

One possibility involves the body’s internal clock.

Bright daytime light is one of the strongest signals the brain uses to regulate circadian rhythms.

These rhythms help control when people feel awake and sleepy, as well as hormone production, metabolism, and other processes tied to physical and mental health.

When people get little bright light during the day, those signals may become weaker.

The researchers found clues suggesting that differences in circadian rhythm and changes in certain brain structures may partly explain the relationship between light exposure and dementia. The association also appeared stronger in some groups, including people with the APOE ε4 genetic variant, a known risk factor for Alzheimer’s disease.

There are plenty of unanswered questions.

Does This Mean Sunlight Prevents Dementia?

Definitely not.

Yes, researchers can say that brighter daytime light was associated with a lower risk of dementia. They cannot say that getting an extra hour of sunshine will prevent Alzheimer’s disease.

Researchers measured light exposure for only seven days, which may not fully reflect someone’s habits over many years. Wrist sensors also measure the light around a person, not exactly how much reaches the eyes.

There could also be other explanations…

People who spend more time outdoors may walk more, socialize more, or have better overall health. Researchers adjusted for many of these factors, but studies like this cannot eliminate every possible difference.

Still, getting more daytime light is a fairly practical habit.

For many people, that might mean taking a morning walk, eating lunch outside, working near a bright window when possible, or simply making a point of getting outdoors during daylight hours.

Some people have fewer opportunities to do that because of work schedules, mobility limitations, caregiving responsibilities, or living situations. That matters too. Daylight exposure is not equally easy for everyone.

No one should view sunlight as a dementia treatment. But alongside exercise, sleep, blood pressure control, social connection, and other established parts of healthy aging, getting out into the daylight may be another small habit worth paying attention to.