A team of scientists led by a UC Berkeley researcher has linked persistent poor sleep to the buildup of a toxic protein that can inhibit the ability to form long-term memory and eventually lead to the onset of Alzheimer’s disease.
A study published Monday by a group led by Bryce Mander, a postdoctoral fellow in the UC Berkeley psychology department, describes how low-quality, disturbed sleep leads to the buildup of the toxic protein beta-amyloid. The study was published online in the journal Nature Neuroscience.
Plaques of beta-amyloid, which have been associated with symptoms of Alzheimer’s, block the transmission of memory from the hippocampus — a region of the brain associated with encoding short-term memories into long-term ones — to the prefrontal cortex, a region associated with long-term, episodic memory.
“Sleep was the missing link between memory, Alzheimer’s and beta-amyloid,” said Vikram Rao, a researcher involved in the study.
The study included testing the ability of 26 healthy adults between the ages of 65 and 81 to memorize 120 pairs of words, in which one word is a normal word and the other a nonsensical word. Mander’s team tested the subjects again after letting them sleep for eight hours and monitored their brain activity while they slept. The subjects underwent a functional MRI scan during their second test to show how much of their short-term memory had been consolidated into long-term memory.
The data, according to Mander, indicated that a lack of deep-sleep waves is associated with a higher level of beta-amyloid and a reduced ability to form long-term memory. This inability stems from the buildup of beta-amyloid, which is flushed out of the brain during periods of deep sleep. Previous research suggested that Alzheimer’s patients had reduced sleep. Adding on to this, Mander said his study shows that beta-amyloid accumulation both promotes and is promoted by lack of sleep.
“Sleep may be a new avenue for (Alzheimer’s) treatments,” Mander said. “If you can intervene and improve sleep, you can help treat Alzheimer’s.”
By drawing attention to sleep as a possible mitigating factor in both the onset and severity of Alzheimer’s, he said, the study introduces a new mechanism for researchers to examine for possible treatments.
“In general, sleep is always being ignored,” Rao said. “Sleep is a very critical factor for good mental health. If you have good sleep, health and hygiene, it will probably mean you’ll have better mental health in later years.”
Mander and his team have already received a grant from the National Institute on Aging to study individual subjects over several years to further examine sleep’s effects on beta-amyloid buildup and Alzheimer’s.