Middle age and older adults who sleep better and for longer durations experience improved cognition than people who sleep for fewer hours, a new study finds.
It has long been established that sleep is a vital factor for the smooth functioning of both the body and the brain. Sleep disorders have been linked to several health issues like obesity and depression. Adding to the benefits of good sleep, a new study found that better sleep quality and sleeping for longer durations boost cognitive abilities among middle-age and older adults.
This is one of the first studies to have looked at more than 30,000 subjects across six middle-income nations (China, Ghana, India, Mexico, the Russian Federation and South Africa). All participants were asked to rate their sleep quality on a scale of five. They were also asked about how many hours they had slept over the previous two nights.
From the first set of data collected, researchers made a few significant observations. The first was that men reported better sleep quality than women in all six nations, Mexico being the highest. Except in Russia and Mexico, women reported sleeping for longer durations than men, with both men and women from South Africa sleeping the longest. Individuals from both genders slept the least in India.
The participants were then asked to take five standard cognitive tests involving immediate recall of a list of presented words, delayed recall of those words later, forward and backward recall of long lists of numbers, and a verbal fluency test in which they listed as many animals as possible without repetition, the use of proper nouns or descriptors. After analysing the test results, researchers found that participants who slept for less than six hours and more than nine hours had significantly lower cognitive scores than participants who got 6 to eight hours of sleep each night.
Researchers also made note of the difference in sleep durations between both sexes. The researchers speculate that women tend to sleep for fewer hours due to postmenopausal changes, increased bladder instability and feelings of isolation after the loss of a spouse or lack of social support.
"Sleep is something that is important but often undervalued in our society," lead author Theresa E. Gildner, a doctoral student in the UO's anthropology department, said in a press statement. "From doing this research and being familiar with the literature, an emphasis on sleep issues by the media in recent years is warranted. Every single piece of evidence that people look at now as they are investigating sleep and different health associations is all showing that sleep really, really, really matters. We're just now scratching the surface on what patterns of sleep normally are, and also what are these associations between sleep and health issues."
According to CDC recommendations, adults, including the elderly should sleep for at least 7 to 8 hours a day. Teens should sleep for 9-10 hours a day and school-aged children should sleep for at least 10 hours a day.
The study was funded by the NIH National Institute on Aging. Findings were published in the June issue of the Journal of Clinical Sleep Medicine.
