30 January 2018

How do you sleep?

Researchers from Washington University in St. Louis have found that circadian rhythm disorders in patients with preclinical stage of Alzheimer's disease (confirmed by brain imaging methods) are a predictor of the imminent appearance of cognitive impairment. In addition, the failure of sleep and wakefulness may increase the risk of the disease in the elderly.

The results of the study will help clinicians identify patients at risk of Alzheimer's disease before the first disorders appear. This is important because the preclinical stage of Alzheimer's can last up to 20 years.

We are not talking about insomnia, but about splitting sleep time into small intervals. For example, 8 hours of sleep per day are divided into 8 episodes of one hour with intervals of wakefulness.

In another study, the group conducted an experiment with mice. He showed that such circadian rhythm disorders accelerate the accumulation of beta-amyloid and the formation of plaques in the brain, which lead to irreversible disorders characteristic of Alzheimer's disease. The mice had their circadian rhythm altered by limiting the activity of the corresponding genes. Two months later, the number of amyloid plaques significantly exceeded that in mice without circadian rhythm disorders.

In previous studies, it has been shown that in humans and animals, the level of beta-amyloid varies depending on the time of day: at night, during sleep, its content is minimal. Violation of night sleep leads to an increase in amyloid levels. It was, among other things, about not deep enough sleep, when it is divided into short intervals with frequent awakenings.

In the new study, the team evaluated the circadian rhythms of 189 patients without cognitive impairment; the average age of participants was 66 years. Some of them underwent positron emission tomography (PET) to search for amyloid plaques in the brain. Others underwent a spinal puncture to search for the pathological beta-amyloid protein in the cerebrospinal fluid. Parts of the patients performed both studies.

All participants kept a special diary in which they recorded their sleep time. In addition, they all wore special devices to assess physical activity.

According to the results of the survey, 139 participants of the study had no signs of illness. The biological clock of most of them worked normally. In some, the change of sleep and wakefulness cycles was disrupted, this was due to old age, nocturnal episodes of apnea or other reasons.

Beta-amyloid or amyloid plaques were found in 50 patients. All of them suffered from significant circadian rhythm disturbances, manifested in a decrease in the rest time received at night and the duration of activity during the day. The analysis, excluding factors such as apnea, age characteristics and others, also showed an increased level of sleep and wakefulness disorders compared to healthy participants.

This study is confirmed by the results of a study on mice: the accumulation of beta-amyloid and the formation of plaques occurs when night sleep is disturbed.

Nevertheless, the authors of the study are in no hurry to link nighttime sleep disorders with the appearance of Alzheimer's disease in healthy people. They call the disruption of the biological clock a biomarker of the preclinical stage of an existing disease. For more information, further study of this problem is necessary.

Article by Erik S. Musiek et al. Circadian Rest-Activity Pattern Changes in Aging and Preclinical Alzheimer's Disease is published in the journal JAMA Neurology.

Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on the materials of Washington University in St. Louis: Body clock disruptions occur years before memory loss in Alzheimer's.

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