Sleeping too much or too little can damage the brain, according to the study

According to a study published Monday in the journal JAMA Neurology, sleep disorders are common at the end of life, according to the study’s authors and associated with changes in cognitive function. (Shutterstock)

ATLANTA: sleep disorder is common at the end of life, the study authors wrote, and was associated with changes in cognitive function: mental ability to learn, think, reason, solve problems, make decisions , remember and pay attention.

Sleep-related changes in sleep have also been linked to the early signs of Alzheimer’s disease, depression, and cardiovascular disease, so the authors investigated possible associations between self-reported sleep duration, demographic and lifestyle factors, subjective and objective cognitive function, and participant levels. of beta-amyloid.

People in the study who reported a short sleep duration (defined in the study as six hours or less) had high levels of beta-amyloid, which “greatly increases” the risk of dementia, the lead author of the study, Joe Winer, a postdoctoral researcher at Stanford University in California, said in an email.

This was compared with participants who reported normal sleep duration, which the study authors defined as seven to eight hours of sleep per night.

Older adults with inadequate sleep also had moderate to significantly worse performance on tests commonly used in older adults to assess cognitive abilities, including orientation, attention, memory, language, and visual-spatial skills; and identify mild dementia.

Too much sleep was also associated with lesser executive function, but those people did not have high levels of beta-amyloid. Participants who reported a long sleep duration (nine or more hours) scored slightly worse on the digit symbol substitution test than those who reported a normal sleep duration. For more than a century, this test has assessed associative learning skills by observing participants ’ability to correctly match symbols with numbers according to a key on the page within 90 to 120 seconds.

“The main takeaway is that it’s important to maintain a healthy sleep late in life,” Winer said in an email. “In addition, both people who slept little and people who slept too much had higher symptoms (body mass index and) more depressive symptoms.” The results suggested that short and long sleep could involve different underlying disease processes, Winer added.

Beta-amyloid 101

Beta-amyloid, or amyloid-β, is “a protein created during the normal activity of brain cells, although we are not yet sure of its function,” Winer said.

“Amyloid-β is one of the first detectable markers in the progression of Alzheimer’s disease,” Winer said. Amyloid plaques are more likely to appear as we age and many people with amyloid accumulated in the brain stay healthy. About 30% of healthy 70-year-olds will have a substantial amount of amyloid plaques in their brains. “

When someone has Alzheimer’s disease, the person’s brain cells that retrieve, process, and store information degenerate and die, according to the Alzheimer’s Association. The “amyloid hypothesis,” one of the main theories about the culprit of this destruction, suggests that the accumulation of the protein may alter communication between brain cells and end their death.

Previous research has suggested that “sleep can help limit amyloid production in the brain and support the drainage system that clears it,” said Laura Phipps, head of communications at Alzheimer’s Research UK, who did not participate in the study, by email.

Amyloid-β can begin to build up many years before obvious Alzheimer’s symptoms manifest, Phipps added. “This makes it difficult to separate cause and effect when studying sleep problems and Alzheimer’s risk, especially if you only look at data at a given time.”

Sleep, depression and sociodemography

The current study looked at 4,417 participants with a mean age of 71.3 years, mostly white and from the United States, Canada, Australia, and Japan.

Both the short-term and long-term groups reported more depressive symptoms than the normal sleep group. Self-reported caffeine intake was not associated with sleep duration. But the more alcoholic beverages participants took daily, the more likely they were to sleep longer.

There were also differences between genders, races, and ethnicities: being female and having had more years of education were significantly related to sleeping more each night. And compared to white participants, black or African American participants reported an average sleep duration of 37.9 minutes less; Asian participants reported 27.3 minutes less; and white Latino or Hispanic participants reported 15 minutes less.

These findings suggest that sleep disparities could be associated with disparities in other aspects of life, such as cardiovascular and metabolic health, socioeconomic factors, and “racial discrimination and perceived racism” correlated with less sleep in previous studies, they wrote. authors.

Remaining questions

“To better understand the order and direction of causality in these relationships, future research will need to build an image of how sleep patterns, biological processes, and cognitive skills change over longer periods of time,” he said. Phipps.

“This new research comes from an extensive international study on cognitively healthy people, but relied on participants to report their sleep duration rather than measuring it directly,” he added. “Researchers were unable to assess sleep quality or time spent at different stages of the sleep cycle, each of which may be an important factor in the link between sleep and cognitive health.”

The authors continued to discuss whether some cognitive domains are more affected by extreme sleep duration than other domains.

Older adults concerned about these findings should consider sleep as important as diet and exercise for their health, Winer said.

“While researchers are still working to understand the complex relationship between sleep and our long-term cognitive health, high-quality sleep can be important to many aspects of our health and well-being,” Phipps said. “The best evidence suggests that between seven and nine hours of sleep is optimal for most adults and anyone who thinks their sleep patterns may affect their long-term health should talk to their doctor.”

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