Scientists are finding there is a big link between sleep and dementia.
During a deep sleep, the human brain appears to wash away the wastes that increase the risk for diseases like Alzheimer’s.
Many new studies have shown that this part of sleep — when the brain follows a steady rhythm and dreams are not common – can help lower levels of tau and beta-amyloid, two hallmarks of dementia.
“This deep sleep is helping protect you somehow,” says Matthew Walker, professor of neuroscience at the UC Berkeley.
The studies come after decades and decades of linking bad sleep to long-term memory and thinking issues, Walker says. “We are now finding there is a major connection between sleep and dementia, especially Alzheimer’s disease.”
The biggest evidence is involving deep sleep, he says. When body temperature drops and the brain starts to create slow, rhythmic electrical waves.
So Walker and his team sought to find out: “Can I estimate how much beta-amyloid you will accumulate over the next five years or more, simply by looking at your sleep?”
Walker’s group then studied 32 patients in their 70s. None of these people had memory problems.
They then used brain scans to watch levels of beta-amyloid in every patient for six years. And the findings, published in the journal Current Biology, revealed that people who got less deep sleep had greater amounts of beta-amyloid.
“We have a specific signature now that lets us better see where you stand on the Alzheimer’s risk chart,” Walker says.
More studies have discovered that the lack of deep sleep is connected to greater levels of tau, which forms tangles within the brain cells of Alzheimer’s patients.
Scientists do have some ideas about why deep sleep lowers both tau and beta-amyloid.
In a groundbreaking study, it was found that the brains of mice switched on “like a dishwasher” during sleep.
“Things like amyloid beta seem to actually be washed away more rapidly when the mice are asleep versus when they’re not asleep,” says Laura Lewis, an assistant professor at Boston University.
“We saw there were fluid waves going through the brain during sleep,” she says. “And it was occurring at a much slower pace than what we saw during wakefulness.”
More than that, each wave was preceded by an electrical wave.
So now researches are searching for ways to create these slow waves that cause deep sleep. “There’s a specific brain structure that if stimulated, can trigger these slow waves in your brain,” she says.
There is some evidence that rhythmic sounds, like that of a box fan, might increase these slow waves.