Can getting quality sleep help prevent Alzheimer's disease?

It's amazing how a good night's sleep can rejuvenate the mind, or "rest the little grey cells" as Hercule Poirot, Agatha Christie's famed sleuth, liked to say.

But sound slumber may boost the brain another way by protecting you against Alzheimer's disease. Research has begun to show an association between poor sleep and a higher risk of accumulating beta-amyloid protein plaque in the brain, one of the hallmarks of the disease.

"Observational studies have found that adults over age 65 with amyloid plaques in their brain have reduced slow-wave sleep, which is thought to play an important role in memory function, even though these people do not yet show signs of Alzheimer's, like memory loss and cognitive decline," says Dr. Brad Dickerson, associate professor of neurology at Harvard Medical School. "It may be that quality sleep could play a role in who may get Alzheimer's."

Sweeping out amyloids

Any talk about Alzheimer's often begins with amyloid proteins. They accumulate in the brain daily and are thought to be a waste product from the energy used when brain cells communicate.

Your brain sweeps out excess amyloid proteins during slow-wave sleep, which is the deep sleep phase during which your memories are consolidated. Some studies suggest that when your sleep gets interrupted during the slow-wave phase, amyloid proteins build up and form plaque on brain tissue. Scientists believe this is the first stage of the development of Alzheimer's, and it can occur years before symptoms appear.

Which comes first

The relationship between poor sleep and amyloid plaque is also a classic chicken-and-egg scenario: does poor sleep cause amyloid plaque, or does plaque buildup cause poor sleep?

It's not clear.

A 2015 study in Nature Neuroscience explored the question by using brain imaging on 26 older adults, ages 65 to 81, who had not been diagnosed with dementia and did not report any sleep problems. First, the group received PET scans to measure levels of amyloid in their brains. Then they were asked to memorize 120 pairs of words and tested on how well they remembered a portion of them.

The people then slept for eight hours, during which their brain waves were measured for sleep disruptions, especially to find out if they awoke during the slow-wave phase. The next morning, their brains were scanned as they tried to recall the memorized words. Over all, the people with the highest levels of amyloid in the brain had the poorest quality of sleep and performed worst on the memory test — some forgot more than half of the information.

Sleep on it

Does all this mean that improving poor sleep or practicing good sleeping habits can protect you against Alzheimer's? Maybe. But it also may mean that quality sleep should be part of a multipronged effort to stave off Alzheimer's, according to Dr. Dickerson.

"Other research has found strong evidence that aerobic exercise also may help to lower a person's risk," he says. "Exercise also helps with better sleep quality, so they may work in conjunction. Weight loss also plays a factor, as people who are overweight tend to have more sleep problems."

Until more is known, Dr. Dickerson suggests that the best approach is to not ignore sleep problems, such as insomnia, sleep apnea, or waking up often to use the bathroom. "See your doctor for an evaluation," he says. It could go a long way toward protecting your little grey cells.