At the end of the day, the sun finally creeps below the horizon line.
And this is precisely the time when 66% of adults not living in long-term care facilities with dementia become more confused and agitated.
This phenomenon is called "sundowning" and it illustrates a complex relationship between our cognitive faculties and sunlight. Sundowning is a common trait associated with people suffering from dementia.
We don't know the exact cause of sundowning, but some experts believe that – in some cases – dementia might impair the part of the brain that produces melatonin.
Melatonin is a hormone that promotes sleep and regulates our circadian rhythms – the body's 24-hour sleep/wake cycle. In the evening, when it's nearing time to sleep, our body increases its production of melatonin to make us drowsy. But dementia can throw off the body's internal clock, so your brain doesn't know when it's time to sleep.
But the answer to getting a dementia patient's circadian rhythm back on track might be sunshine...
This past April, a study published in the American Journal of Clinical Nutrition showed that adults with low levels of vitamin D had a 54% higher risk of developing dementia than those with double that amount of vitamin D.
It's important to note that this was an "association" study. That means researchers found correlation, but not causation. (In other words, two things might happen at the same time, but there's no proof that one causes the other.)
But it reflects similar studies we've seen in the past, which found an association between low levels of vitamin D and an increased risk of dementia.
Dementia is still a largely mysterious disease, so we're always excited to see new research in this area.
And this latest study further confirms what we've said for years...
Get outside and get sunshine.
Vitamin D is called the "sunshine vitamin" because our body naturally converts sunlight to vitamin D.
Aside from its potential to lower dementia risk, vitamin D is essential to many of our body's functions, including building bone strength and supporting the immune system. It's also important in preventing several diseases as well – such as multiple sclerosis and depression. And it's associated with lower rates of pancreatic cancer... one of the deadliest cancers out there.
We get about 50% to 90% of our vitamin D from the sun and the rest from our diet.
That's why I always push folks to get as much sunshine as possible.
But when we look at those with low levels of vitamin D, that doesn't help pinpoint the risk of getting dementia as much. That's because more than 40% of Americans have insufficient levels of vitamin D. About 60% of nursing home residents have lower levels of vitamin D, and folks with more melanin in their skin have lower vitamin D levels, as well.
My take is that it's not low levels of vitamin D alone that put people at higher risk... It's likely one of many factors. The others include co-infections, advanced age, and other medical conditions like diabetes, asthma, and chronic obstructive pulmonary disease.
And it's possible that people with low vitamin D levels also aren't getting as much outdoor activity as they should. That's why I don't just tell folks to sit in front of a light-therapy lamp. I've said for many years, take the time every day to go outside for a walk in the sun...
A 2020 paper in Frontiers in Psychology looked at the effects of being outdoors on our mental and physical state. The researchers analyzed 14 papers and found the following:
Ten to 30 minutes of sitting outside or walking outside in the daylight:
- Lowers heart rate
- Lowers blood pressure
- Lowers levels of the stress hormone cortisol
- Improves scores on mood diagnostics
- Creates more feelings of calmness and restoration
Another study out of the University of Wisconsin School of Medicine and Public Health found an inverse relationship between spending more time in "green space" areas and symptoms of depression, anxiety, and stress. People who spent more time in local gardens or parks reported fewer mental-health symptoms.
And a study from the Journal of Therapeutic Horticulture looked at folks who gardened and those who worked indoors. It found gardeners had significantly lower levels of cortisol. Remember, cortisol is our stress hormone, so higher levels mean more stress and more damaging inflammation.
Spending extended time outside also helps improve our sleep patterns. Exposure to natural light promotes better, deeper sleep. Especially as we experience shorter daylight hours in the fall and winter.
It's one of the reasons I love gardening. I also spend time every day walking outdoors. It's a great combination of benefits: I get to move more, get vitamin D from the sun, and soak up the calming effects of nature.
What We're Reading...
- All about vitamin D.
- Something different: The first stars were disc-shaped.
Here's to our health, wealth, and a great retirement,
Dr. David Eifrig and the Health & Wealth Bulletin Research Team
July 5, 2022