Alzheimer's disease may be related to sleep? Scientists have found the key...

Reviewer of this article: Chen Haixu, Deputy Director and Master Supervisor of the Second Medical Center of PLA General Hospital

For some Alzheimer's (AD) patients, sleep disorders are not only a typical clinical manifestation, but also a harbinger of the development of their disease - sleep problems will appear several years before they confirm that they have been attacked by AD. However, scientists have always been unable to determine what complex and subtle biological/chemical mechanisms are behind this seemingly causal relationship between sleep and dementia?

Not long ago, researchers in the United States published a paper revealing the mystery and explaining how "good sleep health" can help alleviate disease symptoms and reduce the risk of Alzheimer's disease. Their results are also expected to bring new treatments.

The results of the study suggest that the human 24-hour biological clock controls the brain's ability to clear AD-related "stubborn proteins" - beta-amyloid plaques. If this premise is correct, then we can assume that circadian rhythm problems, or sleep disorders, will to some extent lead to the development of Alzheimer's disease; on the other hand, we can also design targeted therapies to delay the progression of this neurodegenerative disease.

"Circadian rhythm disruption is associated with the development of Alzheimer's disease, and sleep disturbance may be an early warning sign of AD," said Jennifer Hurley, a professor at Rensselaer Polytechnic Institute in New York and the lead author of the paper.

Alzheimer's disease occurs when nerve cells in the brain lose connections with each other. The current mainstream scientific judgment is that AD is related to the accumulation of beta-amyloid plaques in the brain and neurofibrillary tangles caused by tau protein. (Most researchers regard the accumulation of beta-amyloid protein as a hallmark of Alzheimer's disease.)

Hurley and colleagues explain their theory this way:

To keep the brain healthy, immune cells called microglia seek out and destroy beta-amyloid that may accumulate in the brain.

This type of glial cell has its own circadian rhythm, so the protein clearance work is also regular; if the rhythm of microglial cells is disrupted, the cleaning process will naturally be greatly affected.
When the clearance of β-amyloid protein loses proper time management, there is a high probability that abnormal plaques will increase in the brains of AD patients.

Although sleep disturbances often precede the onset of AD, Hurley and many other scientists suspect that there is a complex interaction between the two. "Disruptions to sleep and circadian rhythms can lead to the accumulation of beta-amyloid, which in turn damages the brain cells that run the biological clock, leading to further accumulation of protein plaques."

"We've known for a long time that there is a rhythmic clearance of amyloid beta from the brain," Hurley said. "As we age, especially in patients with Alzheimer's disease, this rhythm is lost, with dire consequences."

In view of the above, the author team also gave treatment and prevention strategies:

On the one hand, we could stimulate the brain's ability to clear stubborn proteins through simple interventions, such as exposure to light, or more complex therapies that boost the activity of immune cells.
On the other hand, "cherishing our own sleep and circadian rhythms and giving ourselves a good sleep health may be able to reduce the burden of beta-amyloid."

Source: World Science (ID: World-Science)

Sources:

Study finds link between Alzheimer's and circadian clock

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