A good night's sleep and morning exercise may protect against dementia: changes in the sleep-wake cycle interfere with brain function

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Date: Feb. 1, 2012
From: Duke Medicine Health News(Vol. 18, Issue 2.)
Publisher: Belvoir Media Group, LLC
Document Type: Article
Length: 832 words

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If you tend to wake up early and get in some physical activity during the morning hours, you may be doing much more than getting a good jump on the day: A recent study suggests that you may also be staving off dementia or mild cognitive impairment (MCI).

Research published in the December 2011 issue of Annals of Neurology found that older women with weaker circadian rhythms and who tend to be at their most active later in the day were 80 percent more likely to develop MCI or dementia compared to women with more consistent circadian rhythms and who were active early in the day.

"We've known for some time that circadian rhythms, what some people often refer to as the 'body clock,' can have an impact on our brain and our ability to function normally," says the study's lead author, Greg Tranah, PhD, with the California Pacific Medical Center Research Institute. "What our findings suggest is that future interventions, such as increased physical activity or using light exposure interventions to influence circadian rhythms, could help influence cognitive outcomes in older women."


Circadian rhythms are described as the "physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment," according to the National Institutes of Health. They affect the sleep-wake cycle, temperature, hormone release and many other bodily functions. Research also suggests that circadian rhythms play a role in certain functions of the brain, such as alertness, memory and learning.

Circadian rhythms are controlled by the body's "master clock," which is a collection of thousands of nerve cells in the brain that form the suprachiasmatic nucleus (SCN). The SCN is located in the hypothalamus, near the optic nerve, and is especially sensitive to light. And because the SCN is responsible for the production of melatonin, the hormone that helps you sleep, the more light the SCN is exposed to, the less melatonin is produced. Likewise, as the day gets darker, melatonin production increases to help us sleep at night.

As we age, our circadian rhythms tend to shift toward a more "early to bed, early to rise" pattern, meaning we get sleepier earlier in the evening. And because we tend to need only about seven or eight hours of sleep, that means waking much earlier in the morning.

The study suggests that if your body hasn't made that shift, or if you fight your body's natural desire to go to sleep earlier in the evening and be more active in the morning, your brain may experience changes that could lead to dementia.

"To our knowledge, this is the first study to show such a strong connection between circadian rhythm activity and the subsequent development of dementia or MCI," Dr. Tranah says. "The reasons why this is so are not yet clear. The changes in circadian rhythm may directly influence the onset of dementia or MCI, or the decrease in (physical) activity may be a consequence, a warning sign, if you like, that changes are already taking place in the brain."

He adds that identifying the reason why circadian rhythm might influence cognitive function may lead to developing therapies that could delay or slow down brain problems in older adults.


If you tend to stay up later and are at your most active later in the day, try getting up earlier in the morning. Exercise early and get some sunlight exposure. if not outside, then at least through the windows, to help your body start to shift toward a healthier sleep-wake cycle. Research has shown that Hight exposure and physical in the morning helps set your body's master clock and makes it easier to sleep night.


Sleep-Wake Cycle Linked to Cognitive Problems

"We have known for some time that disturbed activity patterns, most clearly exhibited in sleep-wake patterns, are associated with cognitive performance. Most studies to date, however, have been 'cross-sectional,' and therefore we don't have a clear picture of the direction of the association. Perhaps activity disturbance increases the risk of cognitive problems or the reverse (or both). In this longitudinal study of elderly women in the community, disturbances in the patterns of sleep and activity during a 24-hour cycle (as measured by a wrist monitor) in the cognitively intact increases the risk of future cognitive impairment (dementia). These findings could result from changes in behavior as the authors suggest. If so, potential interventions, such as shifting the sleep-wake cycle, may change these abnormal activity patterns and therefore decrease the risk of cognitive problems. However we must be cautious. Sleep-wake cycle changes may be an early sign of emerging cognitive problems that will lead to dementia regardless of changes in our activity. Even so, developing good sleep and exercise habits is certainly worth the effort."

DANG. BLAZER III, MO, PhD. J.R Gibbons Professor of Psychiatry & Behavioral Sciences; Professor-Department of Community & Family Medicine, Duke

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Source Citation   (MLA 8th Edition)
"A good night's sleep and morning exercise may protect against dementia: changes in the sleep-wake cycle interfere with brain function." Duke Medicine Health News, Feb. 2012, p. 6. Gale OneFile: Health and Medicine, https%3A%2F%2Flink.gale.com%2Fapps%2Fdoc%2FA280006058%2FHRCA%3Fu%3Dtxshracd2588%26sid%3DHRCA%26xid%3Dffa64867. Accessed 20 Oct. 2019.

Gale Document Number: GALE|A280006058