Scientists have found a link between daytime sleep and the development of Alzheimer's disease
Excessive daytime sleep has been shown to lead to the progression of senile dementia. In addition, the annual increase in daytime sleep duration may indicate the progression of the disease.
Older people are known to like to take a nap during the day. But this fact is often ignored by doctors and scientists: little is known about the longitudinal relationship between daytime sleep and cognitive aging. While the effects of daytime naps on the abilities and skills of older adults have been studied, the results of such studies are contradictory. Some show that daytime sleep helps cognitive performance, and also improves mood and gives vigor, while others show that such a habit, on the contrary, has unfavorable consequences for intelligence.
The authors of the new paper, published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association, showed the shortcomings of past studies. For example, that they all assessed participant's sleep by subjective data based on questionnaires. A team of scientists from Harvard Medical School, UCLA and Rush University (USA) decided to conduct a more objective analysis.
They looked at data from 1,401 participants (average age 81 years) of the Rush Memory and Aging Project. Volunteers wore a special device on their wrist, which helped determine the exact duration of their sleep. It turned out that this characteristic, as well as the frequency of sleep is positively correlated with age. In addition, the researchers found a bidirectional longitudinal relationship between daytime sleep and dementia.
That is, longer and more frequent daytime sleep appeared to be a risk factor for developing Alzheimer's disease in normal older adults, both men and women. In addition, the researchers found that the annual increase in the duration and frequency of daytime sleep accelerated as the disease progressed, especially after the clinical manifestation of dementia.
It turns out a vicious circle: the more an elderly person sleeps during the day, the higher his risk of "earn" Alzheimer's disease, and the more rapidly the disease develops, the more frequent and longer daytime sleep.