Heavy deposits of the toxic protein, beta-amyloid, shown in red in the brain on the right, are linked to poor sleep and may be paving the way for Alzheimer's disease. A brain benefiting from deep sleep brain waves and an absence of beta-amyloid is shown on the left.  BRYCE MANDER AND MATTHEW WALKER

New research suggests that a good night's sleep may play an important role in helping protect the brain against memory decline associated with Alzheimer's.

Researchers at the University of California-Berkeley found that a deficit in deep non-REM sleep, a sleep cycle associated with memory retention, was associated with a higher risk of buildup of brain proteins which are believed to play a role in triggering Alzheimer's disease. The buildup of toxic beta-amyloid proteins in the brain then leads to further sleep deprivation, resulting in a vicious cycle.

UC Berkeley neuroscience professor Matthew Walker and colleagues studied 26 cognitively normal older adults and found that higher amounts of beta-amyloid were linked with poor sleep. Participants with the highest levels of beta-amyloid and the poorest quality of sleep also performed worst on memory tests that the researchers gave volunteers before and after sleep.

Past research in mice has shown that deep sleep clears the brain of harmful toxins that accumulate during the day.

The researchers believe this study is an important step in finding ways to prevent memory loss. Over the next five years the team will track a new set of older adults to find out if it's the bad sleep or the bad protein in the brain that begins the cycle of memory loss.