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University of California San Francisco or UCSF: the dangers of dementia

| 27.3.22 |
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University of California San Francisco or UCSF: the dangers of dementia

 Napping is known to be a normal part of the elderly. Even so, based on the results of recent studies this could signal Alzheimer's disease and other dementias. Reporting from the University of California San Francisco or UCSF website, when dementia or signs such as mild cognitive impairment are diagnosed, the frequency or duration of naps increases significantly. The study was led by UCSF and Harvard Medical School in conjunction with Brigham and Women's Hospital. Experts started the study from the theory that napping in the elderly only serves to compensate for a bad night's sleep. 

The study was published in Alzheimer's and Dementia: The Journal of the Alzheimer's Association under the title "Daytime napping and Alzheimer's dementia: A potential bidirectional relationship" on March 17, 2022. "We found the association between excessive daytime napping and dementia persisted after adjusting for quantity and quality of nighttime sleep," Yue Leng, MD, PhD from the UCSF Department of Psychiatry and Behavioral Sciences. "This suggests that the role of naps in itself is important and is independent of nighttime sleep," he continued.
In this study, the researchers used data from 1,401 elderly people who had been followed for up to 14 years by the Rush Memory and Aging Project at Rush Alzheimer's Disease Center in Chicago. Participants were on average 81 years old, three-quarters of whom were women. 

They wear a watch-like device that tracks their mobility. Any prolonged period of inactivity from 9 a.m. to 7 p.m. is defined as a nap. Once a year each participant undergoes a series of neuropsychological tests to evaluate cognition. At the start of the study, 75.7 percent of participants had no cognitive impairment, while 19.5 percent had mild cognitive impairment and 4.1 percent had Alzheimer's disease. For participants who were not cognitively impaired, the daily nap time increased by an average of 11 minutes per year. The rate of improvement doubled after the diagnosis of mild cognitive impairment to a total of 24 minutes and nearly tripled to a total of 68 minutes after the diagnosis of Alzheimer's disease. The researchers looked at the 24 percent of participants who had normal cognition at the start of the study but developed Alzheimer's six years later, and compared with those whose cognition remained stable, they found differences in napping habits. 

Participants who nap more than one hour a day had a 40 percent higher risk of developing Alzheimer's than those who nap less than one hour a day. Then, participants who took a nap at least once a day had a 40 percent higher risk of developing Alzheimer's than those who didn't nap during the day.
This new research confirms the results of a 2019 study. At that time, Leng found an older man who took a two-hour nap a day. These men had a higher chance of developing cognitive impairment than those who nap less than 30 minutes a day. The current study builds on those findings by evaluating naps and cognition annually. According to the researchers, the increased napping could be explained by a further 2019 study by other UCSF researchers. The study compared the postmortem brains of people with Alzheimer's disease with those without cognitive impairment. Those with Alzheimer's disease were found to have fewer wake-promoting neurons in three brain regions. 

These neural changes appear to be related to the tau tangle—a hallmark of Alzheimer's characterized by increased enzyme activity, causing proteins to fail to close and clump together. For information, tau is a protein that helps stabilize the internal framework of nerve cells (neurons) in the brain. This study shows for the first time that naps and Alzheimer's disease drive change in each other in both directions. Yue Leng said it would be interesting for future research to explore whether napping interventions can help slow age-related cognitive decline. "I don't think we have enough evidence to draw a conclusion about a causal relationship, that napping itself causes cognitive aging. However, excessive napping may be a signal of accelerated aging or the cognitive aging process," concluded Yue Leng.


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