We all love the restorative power of a good night’s sleep. Getting a good eight hours is important for so many health reasons. And now researchers at the University of Rochester are suggesting that sleep may also serve as the brain’s “rinse cycle” by removing harmful proteins that develop between brain cells while we’re awake.
Differences in sleep patterns already have been linked to Alzheimer’s disease. The Alzheimer’s Association (AA) points out that people who have Alzheimer’s disease often experience problems with sleeping, including changes in their sleep schedule. These changes are believed to result from the impact of Alzheimer’s on the brain. While many older adults do notice changes in their sleep patterns and quality, the disturbances are more frequent and severe in a person who has Alzheimer’s. AA points out that some researchers have found changes in sleep patterns in the early stages of the disease; evidence also exists that these changes are much more common in the later stages.
The sleep changes include:
- Waking up often and staying awake longer: People with Alzheimer’s also spend less time in the dream and non-dreaming sleep stages.
- More sleeping during daytime hours: Some studies have found that people in the later stages of Alzheimer’s sleep a significant part of the day; they may spend up to 40 percent of nighttime awake. In some cases, people with Alzheimer’s stay up all night and then sleep all day.
The new research offers some interesting insight into the inner workings of the brain. The University of Rochester researchers looked at the flow of the brain’s cerebrospinal fluid in mice, using high-tech imaging. They found that the cerebrospinal fluid circulated at a more rapid pace while the mice were asleep.
Furthermore, the study found that the mice brain cells actually contracted while they slept, which expanded the area between cells by up to 60 percent. This process allowed the fluid to move around more easily in order to wash away waste proteins--such as beta amyloid--that form the sticky plaques in Alzheimer’s disease. These waste proteins are poisonous to the brain’s cells. The brain cells then returned to normal size once the mice awoke, causing the flow of the cerebrospinal fluid to slow between the cells.
Researchers surmise that this cleaning process, called the glymphatic system and which has also been seen in research in the brains of rats and baboons, is primarily done during the night because of the energy required to carry it out. "It's probably not possible for the brain to both clean itself and at the same time [be] aware of the surroundings and talk and move and so on," said Dr. Maiken Nedergaard, a professor of neurosurgery at the University of Rochester and an author of the study.
Some experts suggest that this research may offer a new approach in the battle against Alzheimer’s. “It does raise the possibility that one might be able to actually control sleep in a way to improve the clearance of beta amyloid and help prevent amyloidosis that we think can lead to Alzheimer's disease,” said Dr. Randall Bateman, a professor of neurology at Washington University.