NEUROLOGY

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Is Lack of Sleep a Risk Factor for Alzheimer’s Disease?

 

According to an article published online in the¬†Proceedings of the National Academy of Sciences. (9 April 2018), losing just one night of sleep led to an immediate increase in beta-amyloid. The study is among the first to demonstrate that sleep may play an important role in human beta-amyloid clearance. Beta-amyloid is a metabolic waste product present in the fluid between brain cells. In Alzheimer’s disease, beta-amyloid proteins clump together to form amyloid plaques, a hallmark of the disease, negatively impacting communication between neurons. While acute sleep deprivation is known to elevate brain beta-amyloid levels in mice, less is known about the impact of sleep deprivation on beta-amyloid accumulation in the human brain.

 

To understand the possible link between beta-amyloid accumulation and sleep, the authors 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 after sleep deprivation (being awake for about 31 hours). Results showed that beta-amyloid increased¬†about 5% after losing a night of sleep in brain regions including the thalamus and hippocampus, regions especially vulnerable to damage in the early stages of Alzheimer’s disease.

 

In Alzheimer’s disease, beta-amyloid is estimated to increase about 43% in affected individuals relative to healthy older adults. However, it is unknown whether the increase in beta-amyloid in the study participants would subside after a night of rest. Interestingly, the study also found that study participants with larger increases in beta-amyloid reported worse mood after sleep deprivation. According to the authors, even though the sample was small, the study demonstrated the negative effect of sleep deprivation on beta-amyloid burden in the human brain and that future studies are needed to assess the generalizability to a larger and more diverse population. It is also important to note that the link between sleep disorders and Alzheimer’s risk is considered by many scientists to be “bidirectional,” since elevated beta-amyloid may also lead to sleep disturbances.

 

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