By triggering a brain-clogging compound that in turn interrupts sleep, poor sleep may increase people’s risk of Alzheimer’s disease, new research suggests. Sleep disruption could be one of the missing pieces in the puzzle of how a protein called beta-amyloid starts its damage long before people have trouble with memory, researchers reported.
Dr. Matthew Walker of the University of California, Berkeley, who presented the data at the Alzheimer’s Association International Conference, linking amyloid levels with people’s sleep and memory performance, said:
“It’s very clear that sleep disruption is an underappreciated factor. It’s a new player on the scene that increases risk of Alzheimer’s disease. Sleep is a modifiable factor. It’s a new treatment target."
Even for general health, getting enough sleep is important. Seven to eight hours a night are recommended for adults.
But scientists have long known that people who don’t get enough have trouble learning and focusing. And anyone who’s cared for someone with dementia knows the nightly wandering and other sleep disturbances that patients often suffer, thought to be a result of dying brain cells.
Sleep problems, the new research suggests, actually interact with some of the disease processes involved in Alzheimer’s, and those toxic proteins further affect the deep sleep that’s so important for memory formation.
Two sleep studies tracked nearly 6,000 people over five years, and found that those who had poor sleep quality were more likely to develop mild cognitive impairment, early memory problems that sometimes lead to Alzheimer’s, said Dr. Kristine Yaffe of the University of California, San Francisco.
Sleep apnea, brief interruptions of breathing that repeatedly awaken people without them realizing, caused a nearly two-fold increase in that risk, Yaffe said. She recommended that people at risk of Alzheimer’s be screened for sleep disorders, especially apnea, which can be effectively treated.
Clues to the biology behind these changes come from previous animal studies. Dr. David Holtzman of Washington University in St. Louis reported a series of mice experiments that found amyloid production is highest during waking hours and lowest during deep sleep.
Depriving mice of sleep triggered toxic amyloid build-up. And once those deposits began, the mice stayed awake longer on their own. Holtzman also checked Alzheimer’s other bad actor, the protein tau that forms tangles in the brain, and found the same effect on deep sleep.
Over 5 million Americans currently have Alzheimer’s. That number is expected to more than double by 2050.
Alterations that lead to Alzheimer’s can begin up to 20 years before memory lapses, and scientists are now studying drugs in people at high risk in hopes of finding preventive treatment.
“There are lots of risk factors we might be able to change. Sleep is one,” said Alzheimer’s Association chief science officer Maria Carrillo. Together, she said, the new research emphasizes how “sleep is critical as we age.”
Image: Rowena Dugdale, Wellcome Images