The study, which was published in the journal Science Translational Medicine, involved researchers from the Washington University School of Medicine (WUSM) in St. Louis.
Slow-wave sleep, tau, and amyloid plaque
Common complaints among the elderly include having trouble sleeping and waking up frequently during the night, but experts believe that these issues could also be linked to a risk of developing Alzheimer’s.
Dr. Brendan Lucey, the lead author and an assistant professor of neurology at WUSM, explained that this study is the first of its kind to reveal a link between slow-wave sleep (SWS) and tau in very early Alzheimer’s.
Slow-wave sleep refers to the sleep phase humans need to enter to wake up feeling rested. Dreaming and sleepwalking may occur during SWS. Experts believe that SWS is essential for memory consolidation.
Tau is a brain protein that is linked to Alzheimer’s. This brain protein may form tangles in areas of the brain that are critical for memory. As Alzheimer’s progresses, tau and amyloid beta (another protein) gradually spread across the brain. Fortunately for us, the brain has a way of regularly flushing out these memory-robbing proteins.
Dr. Alex Dimitriu, who is double board-certified in psychiatry and sleep medicine and the founder of Menlo Park Psychiatry & Sleep Medicine, said data suggests that during sleep, "the brain can shrink substantially as it clears built-up toxins, which include tau and amyloid.
Poor sleep quality and risk of Alzheimer's
To determine if there is a link between deep sleep and Alzheimer’s, researchers monitored 119 participants aged 60 or older. The group included individuals who had none or very mild cognitive decline while they were in their homes.
All of the volunteers were given a portable brain-wave monitor and a wrist-worn movement tracker for the duration of the study. For one week, the participants were instructed to track their nighttime sleep sessions and daytime napping.
Lucey, who is also the director of the Washington University Sleep Medicine Center, said that during sleep, the brain cycles through different stages, one of which is SWS. Good quality sleep is essential for your overall health, and it is thought to be important for preserving memory.
For the study, the researchers measured amyloid beta and tau levels in the brain and spinal fluid of the volunteers. The research team considered the participants' age, gender, and movement while sleeping.
The findings revealed that less slow-wave sleep is linked to more tau protein in the brain and a higher ratio of tau to amyloid beta in the spinal fluid.
Poor sleep negatively affects your health
The National Sleep Foundation noted that sleep triggers changes in the brain that strengthen memory. The group also warned that the loss of even a half night’s sleep can affect brain function. (Related: Experts warn that it just takes ONE sleepless night to dramatically increase your risk of Alzheimer’s.)
Dr. Dimitriu shared that this could be due to the brain’s waste-clearing system, which is active during SWS. This period of deep sleep usually takes place during the first half of the night. He added that when you lack deep or slow-wave sleep, you may have elevated levels of tau and amyloid beta.
According to the Centers for Disease Control and Prevention (CDC), a whopping 29 to 44 percent of individuals in the U.S. get less than the recommended seven to eight hours of sleep every night. The average American often stays up late to study, work, or socialize.
However, this needs to stop if people want to avoid serious health conditions. Poor sleep quality can significantly increase the risk of developing various health problems.
- It can increase your risk of diabetes – Data from a short-term sleep restriction study suggest that healthy volunteers who only had four hours of sleep each night processed glucose more slowly than they when they were permitted to sleep for up to 12 hours.
- It may cause obesity – Poor sleep is associated with lower levels of leptin. This hormone tells your brain that you're already full. Insufficient sleep may also increase the levels of ghrelin, a hormone that triggers hunger. If you don't get enough sleep, you may experience food cravings even after you've already eaten enough.
- It can increase your risk of high blood pressure (hypertension) or heart disease – Research reveals that getting less than six hours of sleep may cause or aggravate high blood pressure. This could explain the link between poor sleep and heart disease or stroke.
If you want to lower your risk of Alzheimer's or other conditions like diabetes, obesity, or heart disease, make positive lifestyle changes. Stay active, follow a healthy diet, and get at least eight hours of sleep every night to boost your brain health.
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