Losing just one night’s sleep causes an immediate increase in beta-amyloid, proteins in the brain that clump together to form brain plaques characteristic of Alzheimer’s disease, say researchers at the National Institutes of Health (NIH).
While studies have found that acute sleep deprivation causes an increase in beta-amyloid levels in mice, evidence has been less compelling in humans. The new study is the first to show that sleep helps to clear beta-amyloid, a metabolic waste product present in the fluid between brain cells, from the human brain.
“This research provides new insight about the potentially harmful effects of a lack of sleep on the brain and has implications for better characterizing the pathology of Alzheimer’s disease,” said George F. Koob, Ph.D., director of the National Institute on Alcohol Abuse and Alcoholism (NIAAA), part of the National Institutes of Health, which funded the study.
The researchers used positron emission tomography (PET) to scan the brains of 20 healthy subjects, ranging in age from 22 to 72, after a night of rested sleep and then after they had been awake for about 31 hours.
They discovered increases in beta-amyloid of about five percent in the brain. Affected regions included the thalamus and hippocampus, which are areas especially vulnerable to damage in the early stages of Alzheimer’s disease.
In Alzheimer’s disease, scientists estimate that levels of beta-amyloid increase about 43 percent in comparison to healthy older adults.
The researchers don’t know if the increase in beta-amyloid would diminish after a night’s rest. They also noted that the link between Alzheimer’s and sleep disorders is “bidirectional” since elevated beta-amyloid is also linked to sleep disturbances.
“Even though our sample was small, this study demonstrated the negative effect of sleep deprivation on beta-amyloid burden in the human brain,” said Dr. Shokri-Kojori.
The study was published in the Proceedings of the National Academy of Sciences.
A recent study from the Mayo Clinic found that being sleepy during the day may be a warning sign that a senior is at risk of developing Alzheimer’s.
Researchers studied adults 70 years and older without dementia. Imaging scans were done at the beginning of the study and at least once more during the next seven years. Later scans showed that those who reported being very sleepy during the day — 22.3 percent — had accumulations of beta amyloid in areas of the brain associated with Alzheimer’s.
Too much sleep also appears to be bad for aging brains. A 2017 study published in the journal Neurology found that people who slept for more than nine hours a night had smaller brains than those who slept less. In addition, their risk of developing dementia within 10 years was a whopping six times higher than for those who slept less than nine hours.
Alzheimer’s disease, which is a form of dementia, is the fifth leading cause of death among people 65 years of age and older, according to the Centers for Disease Control and Prevention, and death rates are climbing. Between 1999 and 2014, death rates increased 55 percent.
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