Poor sleep could increase risk of developing Alzheimer's – study
Researchers at the University of California Berkeley have found that a deficit in deep non-REM (Rapid Eye Movement) sleep is associated with a higher risk of beta-amyloid protein build-up in the brain – the type of protein believed to attack the brain's long-term memory and trigger Alzheimer's diseas
Those higher levels of memory-robbing proteins then cause further sleep disruption – resulting in a vicious cycle.
“The more beta-amyloid you have in certain parts of your brain, the less deep sleep you get and, consequently, the worse your memory,” researcher and UC Berkeley neuroscience professor Matthew Walker said.
“Additionally, the less deep sleep you have, the less effective you are at clearing out this bad protein. It’s a vicious cycle.”
The study's lead author, Bryce Mander, said the study's data is “very suggestive that there's a causal link” between poor sleep and beta-amyloid protein.
"If we intervene to improve sleep, perhaps we can break that causal chain,” he said.
The team's findings were published Monday in the journal Nature Neuroscience.
The study consisted of 26 healthy adults aged 65 to 81, who showed no evidence of dementia or other neurodegenerative, sleep, or psychiatric disorders. They each received scans to measure the amount of beta-amyloid in their brains.
They were then asked to memorize 120 pairs of words, and were tested on how well they remembered a portion of them.
The participants then slept for eight hours, during which their brain waves were measured. The next morning, their brains were scanned as they recalled the remaining word pairs.
Researchers tracked activity in the hippocampus – the area where memories are temporarily stored before moving to the prefrontal cortex.
“The more you remember following a good night of sleep, the less you depend on the hippocampus and the more you use the cortex,” Walker said. “It’s the equivalent of retrieving files from the safe storage site of your computer’s hard drive, rather than the temporary storage of a USB stick.”
The results showed that those with the highest levels of beta-amyloid in the medial frontal cortex had the poorest quality of sleep and performed worst on the memory test the following morning. Some forgot more than half the information they had learned the day before.
But despite the researchers' conclusion that the bad protein and poor sleep lead to a “vicious cycle,” it remains unclear which one begins the cycle. This will be the foundation of further research, as scientists set out to track a new set of older adults over the next five years.
"This is a new pathway linking Alzheimer's disease to memory loss, and it's an important one because we can do something about it," Mander said.
Alzheimer's is the most common form of dementia, accounting for 60 percent to 80 percent of cases of the condition. Nearly 44 million people are currently living with the disease, according to Alzheimer's Disease International.
As the Baby Boomer generation continues to age, Alzheimer's is expected to become one of the world's fastest-growing and most debilitating public health concerns.