(CNN) – How long older adults sleep could affect their brain health, according to a study published Monday in the journal JAMA Neurology.
Sleep disorders are common in late life, the study authors wrote, and are associated with changes in cognitive function – the mental ability to learn, think, think, problem-solve, decide, remember, and pay attention.
Age-related changes in sleep have also been linked to early signs of Alzheimer’s, depression, and cardiovascular disease. Therefore, the authors examined possible associations between self-reported sleep duration, demographic and lifestyle factors, subjective and objective cognitive function, and participants’ levels of beta-amyloid.
Those in the study who reported short sleep times – defined in the study as six hours or less – had elevated levels of amyloid beta, which “greatly increased” their risk of dementia, said lead author Joe Winer Postdoctoral fellow at Stanford University in California, via email.
That was compared to participants who reported a normal sleep duration, which the study authors defined as seven to eight hours of sleep per night.
The older adults with inadequate sleep also performed moderately to significantly worse on tests commonly used in older adults to assess cognitive abilities, including orientation, attention, memory, language, and visuospatial skills; and recognize mild dementia.
Too much sleep was also linked to decreased executive function, but these people did not have elevated beta-amyloid levels. Participants who reported long sleep times (nine or more hours) performed slightly worse on the number symbol replacement test than those who reported normal sleep time. For more than a century, this test has assessed associative learning skills by observing test takers’ ability to correctly map symbols to numbers using a key on the page within 90 to 120 seconds.
“The most important takeaway is that it is important to maintain a sound sleep late in life,” Winer said via email. “Also, people who got too little sleep and people who got too much sleep had higher (body mass index and) more depressive symptoms.” The results suggested that short and long sleep may involve different underlying disease processes, Winer added.
Amyloid beta 101
Beta-amyloid, or amyloid-β, is “a protein made during normal brain cell activity, although we are still unsure of its function,” said Winer.
“Amyloid-β is one of the first detectable markers for Alzheimer’s disease progression,” said Winer. Amyloid plaques are more common with age, and many people with amyloid buildup in their brains stay healthy. About 30% of healthy 70 year olds have significant amounts of amyloid plaques in their brain. “
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 leading theories as to who is to blame for this destruction, suggests that the accumulation of the protein could disrupt communication between brain cells and eventually kill them.
Previous research has shown that “sleep can both help limit the production of amyloid in the brain and help the drainage system that clears it,” said Laura Phipps, director of communications at Alzheimer’s Research UK, who was not involved in the study was involved. by email.
Amyloid-β can build up many years before any obvious Alzheimer’s symptoms appear, Phipps added. “This makes it difficult to identify cause and effect when studying sleep problems and Alzheimer’s risk, especially when looking at data from one point in time.”
Sleep, Depression, and Sociodemography
The current study analyzed 4,417 participants with a mean age of 71.3 years, mostly white and from the US, Canada, Australia and Japan.
Both the short and long sleep groups reported more depressive symptoms than the normal sleep group. Self-reported caffeine intake was not linked to length of sleep. But the more alcoholic beverages participants drank each day, the more likely they were to sleep longer.
There were also gender, race, and ethnicity differences: being female and having more years of education were both significantly linked to sleeping longer each night. And when compared to white participants who reported an average sleep duration of seven hours and nine minutes, Winer, black or African American participants reported an average sleep duration of 37.9 minutes less. Asian participants reported 27.3 minutes less than white participants, and Latin American or Hispanic white participants reported 15 minutes less.
These results suggest that sleep differences may be linked to differences in other aspects of life, such as cardiovascular and metabolic health, socioeconomic factors, and “racial discrimination and perceived racism,” which in previous studies correlated with less sleep, the authors wrote .
“To better understand the order and direction of causality in these relationships, future research needs to create a picture of how sleep patterns, biological processes, and cognitive abilities change over time,” said Phipps.
“This new study comes from a large, international study of cognitively healthy people, but it relied on participants reporting how long they slept rather than measuring it directly,” she added. “Researchers were unable to assess the quality of sleep or the amount of time spent at different stages of a sleep cycle, each of which can be an important factor in the link between sleep and cognitive health.”
Whether some cognitive domains are more affected by extreme sleep duration than other domains also remains controversial, the authors write.
Older adults who are concerned about these results should consider sleep as just as important to their health as diet and exercise, Winer said.
“While researchers are still working to understand the complex relationship between sleep and our long-term cognitive health, quality sleep can be important to many aspects of our health and wellbeing,” said Phipps. “The best evidence suggests that seven to nine hours of sleep is optimal for most adults, and anyone who believes their sleep pattern is affecting their long-term health should speak to their doctor.”
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