Adequate amount of sleep is linked to brain health, study says

The amount of sleep of adults over 70 years old can affect the health of the brain, according to a study published on Monday (30) in the journal JAMA Neurology. According to the authors, interrupted sleep is common in old age and is associated with changes in cognitive function – the mental ability to learn, think, reason, solve problems, make decisions, remember and pay attention.

Age-related sleep changes have also been associated with early signs of Alzheimer’s disease, depression, and cardiovascular disease. Therefore, the authors investigated possible associations between self-reported sleep duration, demographic and lifestyle factors, subjective and objective cognitive function, and beta amyloid levels – a marker of Alzheimer’s disease.

Study participants who reported a short sleep duration — defined as six hours or less — had elevated levels of beta amyloid, which “greatly increases” the risk of dementia, lead author Joe Winer said in an email. , postdoctoral researcher at Stanford University in California. This compared to participants who reported sleep duration of seven to eight hours per night, considered the normal duration.

Elderly people with inadequate sleep also performed moderately to significantly worse on tests commonly used in this age group to assess cognitive abilities, including orientation, attention, memory, language, visuospatial skills, and identification of mild dementia.

Sleeping a lot was also associated with lower executive functions, but these 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 duration.

For more than a century, this test has assessed associative learning skills, looking at participants’ ability to correctly match symbols and numbers over a period of 90 to 120 seconds.

“The main lesson is that it’s important to maintain healthy sleep at the end of life,” Winer said via email. “In addition, both people who sleep too little and people who sleep too much had higher body mass index and more depressive symptoms.” The findings suggest that short and long sleep may involve different underlying disease processes, Winer added.

Beta Amyloid 101

Beta amyloid, or β-amyloid, is a protein created during normal brain cell activity, although we’re still not sure of its function, according to Winer. “It is one of the first detectable markers ‘in the progression of Alzheimer’s disease’, he says.

The expert explains that amyloid-β proteins begin to accumulate throughout the brain, adhering to plaques. Amyloid plaques are more likely to appear with age, and many people with amyloid accumulated in the brain remain healthy. “About 30% of healthy people aged 70 years and over will have substantial amounts (of) amyloid plaques in their brains,” he says.

When someone has Alzheimer’s disease, their brain cells that retrieve, process and store information degenerate and die, according to the Alzheimer’s Association. The “amyloid hypothesis,” one of the leading theories as to who is responsible for this destruction, suggests that the accumulation of the protein can interrupt communication between brain cells, eventually killing them.

Previous research has suggested that sleep may help limit amyloid production in the brain and support the drainage system that cleans it, according to Laura Phipps, head of communications for Alzheimer’s Research UK, who was not involved in the study.

β-amyloid can begin to accumulate many years before obvious Alzheimer’s symptoms appear, 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 point-in-time data.”

Sleep, depression and sociodemographic data

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

There were also differences between genders, races and ethnicities: being a woman and having more years of education were both significantly associated with sleeping more every night. And when compared with white participants who reported an average sleep duration of seven hours and nine minutes, black or African American participants reported an average sleep duration of 37.9 minutes less. Asian volunteers reported 27.3 minutes less than whites, and Hispanic or Hispanic whites reported 15 minutes less.

These findings suggest that sleep disparities may 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, the authors wrote.

unanswered questions

“To better understand the order and direction of causality in these relationships, future research will need to build a picture of how sleep patterns, biological processes and cognitive abilities change over long periods of time,” said Phipps. “This new research is from a large international study of cognitively healthy people, but it relied on participants to report their sleep duration rather than directly measuring it,” he added.

“Researchers could not assess the quality of sleep or the time spent at different stages of the sleep cycle. Each of these can be an important factor in the link between sleep and cognitive health. Seniors concerned about these findings should consider sleep as important as diet and exercise for health,” said Winer.

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

(Translated text. Read the original in English.)