Researchers say lack of sleep can cause a buildup of certain proteins in the brain.
Having a hard time getting a good night’s sleep? If you’re older, it could mean more than just a rough start to the day.
While having trouble getting to sleep and waking up frequently during the night are common to aging, these issues are also seen as a risk for Alzheimer’s disease.
Researchers at Washington University School of Medicine in St. Louis say that older people who spend less time in slow-wave sleep — the sleep phase you need to wake up feeling rested — show increased levels of a brain protein called tau that’s associated with Alzheimer’s disease.
“Our project is the first to show an association between slow-wave sleep and tau in very early Alzheimer’s disease,” said Dr. Brendan Lucey, an assistant professor of neurology, director of the Washington University Sleep Medicine Center, and lead author of the study.
Tau can form tangles in areas of the brain critical for memory. As Alzheimer’s disease progresses, this protein and another called amyloid beta slowly spread through the rest of the brain.
But the brain has a way to regularly flush out these memory-robbing proteins.
“Research shows that during sleep the brain can shrink substantially as it clears built-up toxins, tau, and amyloid among them, Dr. Alex Dimitriu, who is double board-certified in psychiatry and sleep medicine and the founder of Menlo Park Psychiatry & Sleep Medicine, told Healthline.
To confirm the link between deep sleep and Alzheimer’s disease, researchers monitored 119 people age 60 or older who had no or very mild cognitive decline while they were in their homes.
Each participant was given a portable brain-wave monitor and a wrist-worn movement tracker for the one-week study. They were asked to keep track of nighttime sleep sessions and daytime napping.
“During sleep, the brain cycles through different stages, and slow-wave sleep is one of them,” Lucey said. “It’s necessary to have good-quality sleep and is thought to be important for preserving memory.”
The researchers also measured amyloid beta and tau levels in the brain and spinal fluid of the participants.
After factoring in age, gender, and movement while sleeping, the study showed that less slow-wave sleep was associated with more tau protein in the brain and a higher ratio of tau to amyloid beta in spinal fluid.
According to the National Sleep Foundation, sleep triggers changes in the brain that strengthen memory, and loss of even a half night’s sleep can impair brain function.
Dimitriu said this may be because the brain’s waste-clearing system is specifically active during slow-wave sleep, a period of deep sleep that often comes in the first half of the night.
“When people lack deep or slow-wave sleep, they can have elevated levels of tau and amyloid beta. Older people with dementia are often known to have a symptom called ‘sundowning,’ where mental processes and awareness diminish as the day wears on,” he explained.
“This may be a direct consequence of the buildup of these toxins during the day.”
Americans tend to stay awake at night studying, working odd hours, or socializing. But skipping sleep can come with serious health consequences.
Sleep loss can increase the risk of developing various health problems, some potentially life-threatening.
“Sleep is essential to forming memory and creating new room for learning to occur. People who are sleep deprived are more prone to worsening depression or lack of adequate response to treatment for it,” Dimitriu said.
“Aside from a buildup of toxins, insufficient sleep can also affect mood, memory, metabolism, and the immune system.”
Here’s some of the health effects.
- Lack of sleep can cause obesity. Insufficient sleep is linked to lower levels of the hormone leptin, which alerts the brain that a person has eaten enough. It can also increase levels of ghrelin, a hormone that triggers hunger. Poor sleep could bring on food cravings even after a person has already eaten enough.
- There may be an increased risk of diabetes. A short-term sleep restriction study found that healthy participants who had their sleep reduced to four hours per night processed glucose more slowly than they did when they were permitted to sleep up to 12 hours.
- It can set the stage for high blood pressure or heart disease. Research finds that less than six hours of sleep can cause or worsen high blood pressure. This may help explain the association between poor sleep and heart disease or stroke.
New research shows that people who don’t get enough time in a sleep stage called slow-wave sleep can have higher levels of a protein called tau that’s associated with cognitive decline and Alzheimer’s disease.
Up to 44 percent of Americans get less than the recommended seven to eight hours of sleep each night.
While previous research has shown a link between poor sleep and brain changes that may lead to Alzheimer’s disease, this is the first study to show that less slow-wave sleep increases tau levels in early Alzheimer’s disease.
Insufficient sleep doesn’t only affect memory. It may cause other serious health problems including obesity, diabetes, heart disease, or stroke.