Anyone who has ever worked all night can attest how vital sleep can be for your ability to function throughout the day. You can feel terrible and have trouble concentrating on the task at hand if you aren’t getting enough sleep.
Researchers have known for years that the mysteries surrounding sleep are not unsolved. Sleep is vitalto improve immune function, metabolism and memory. Research suggests that adults should sleep for at most seven hours per night. Eight hours per eveningTo work optimally.
A recent study however, published in the journal BrainThe Washington University School of Medicine suggests that sleep is important. You can alsoToo much can have negative consequences.
The Study
The Washington University School of Medicine research team wanted to find out how sleep and cognitive impairment were related over time. As both poor sleep and Alzheimer’s disease are associated with cognitive decline, researchers selected older adults for their sample. For a period of 4 to 5 years, 100 participants were tracked in terms of cognitive function.
Alzheimer’s is the most common cause of cognitive decline among older people, accounting for 70% of cases of dementia. Furthermore, Insufficient sleep can make the disease worsePoor sleep is a common symptom.
Although separating out the effects of poor sleep and Alzheimer’s can be challenging, using this sample made the task more manageable. As reported on, SciTechDaily, “By tracking cognitive function in a large group of older adults over several years and analyzing it against levels of Alzheimer’s-related proteins and measures of brain activity during sleep, the researchers generated crucial data that help untangle the complicated relationship among sleep, Alzheimer’s, and cognitive function.”
The study’s beginning 88 participantsWhile 12 people with cognitive impairment showed no signs, none of them had dementia. One of the 12 participants with cognitive impairment had mild dementia while the 11 others had pre-dementia. Although only a few participants showed signs of dementia, all were asked to complete both cognitive and neuropsychological tests that carefully separated the effects of sleep from Alzheimer’s disease.
In this study, participants were asked to give blood samples for testing for the high-risk Alzheimer’s genetic variant APOE4. In addition, they also provided samples of cerebrospinal fluid to measure Alzheimer’s protein levels. A tiny EEG monitor was also attached to the participants’ foreheads for four or six nights to measure brain activity while they slept.
After analysing all data, scientists discovered that cognitive scores decreased for those who slept less then 4.5 hours. OderOver 6.5 hours of sleep per night. These results suggest that sleep quality may be more important than total sleep time.
Researchers Believe “Sleep Quality” Could Be Key To A Good Night’s Rest
Brendan Lucey, associate professor of neurology and director at the Washington University Sleep Medicine Center Brendan Lucey wrote, “Our study suggests that there is a middle range, or ‘sweet spot,’ for total sleep time where cognitive performance was stable over time.” Researchers observed a U-shaped relationship between sleep and cognitive decline.
The U-shaped relationship remained stable even after taking into account specific sleep phases such as dream, rapid-eye-movement and non-REM. Furthermore, the relation held up when adjusting for factors such as age, sex, the presence of Alzheimer’s protein, and the presence of APOE4.
According to the EEG, those who slept longer than 6.5 hours or less than 4 hours per night were more susceptible to cognitive decline. Dr. Lucey pointed out that those whose scores fell in the middle range remained stable. “sweet spot.”
Neurology professor and co-senior author David Holtzman MDThis is what the study explains. “It was particularly interesting to see that not only those with short amounts of sleep but also those with long amounts of sleep had more cognitive decline.”Dr. Holtzman stated that, “It suggests that sleep quality may be key, as opposed to simply total sleep.”
Dr. Lucey echoes these sentiments claiming: “Short and long sleep times were associated with worse cognitive performance, perhaps due to insufficient sleep or poor sleep quality.”Despite these encouraging results, Dr. Lucey still believes that the fascinating connection between sleep and cognitive functioning is at best murky.
“An unanswered question is if we can intervene to improve sleep, such as increasing sleep time for short sleepers by an hour or so, would that have a positive effect on their cognitive performance so they no longer decline?”Dr. Lucey asked. For a better understanding of the question, researchers will need to collect more longitudinal and/or repeat observations over a certain period of time.
Dr. Lucey suggests that people continue to have short and long sleep patterns as long as they feel well-rested.