Newswise — Sound sleep in young and middle-aged people helps memory and learning, but as they hit their seventh, eighth and ninth decades — and generally don’t sleep as much or as well — sleep is not linked so much to memory, a Baylor University researcher says.
The research raises an “alluring question,” said Michael K. Scullin, Ph.D., director of Baylor's Sleep Neuroscience and Cognition Laboratory, who examined 50 years of sleep research for an article in the journal Perspectives on Psychological Science.
“If sleep benefits memory and thinking in young adults but is changed in quantity and quality with age, then the question is whether improving sleep might delay — or reverse — age-related changes in memory and thinking,” said Scullin, assistant professor of psychology and neuroscience in Baylor’s College of Arts & Sciences.
“It’s the difference between investing up front rather than trying to compensate later,” he said. “We came across studies that showed that sleeping well in middle age predicted better mental functioning 28 years later.”
The article — “Sleep, Cognition, and Normal Aging: Integrating a Half Century of Multidisciplinary Research” — notes that the benefits of a sound night’s sleep for young adults are diverse and unmistakable. One example is that a particular kind of “deep sleep” called “slow-(brain)-wave-sleep” helps memory by taking pieces of a day’s experiences, replaying them and strengthening them for better recollection.
By the time people reach middle age, more sleep during the day, such as an afternoon nap, also helps people’s memory and protects against its decline — as long they don’t skimp on nighttime sleep.
But as they grow older, people wake up more at night and have less deep sleep and dream sleep — both of which are important for overall brain functioning, Scullin said. Researchers’ extensive review began with studies as long ago as 1967, including more than approximately 200 studies measuring sleep and mental functioning. Participants ages 18 to 29 were categorized as young; ages 30 to 60 as middle-aged; and older than 60 as old.
Participants were asked how many hours they typically slept, how long it takes them to go to sleep, how often they wake in the middle of the night and how sleepy they feel during the day. The research also correlated results from numerous brain-wave studies and experiments dealing with sleep deprivation, napping and sleep intervention, such as sleep medications.
Scullin noted that if a person lives 85 years, he or she may sleep nearly 250,000 hours – more than 10,000 full days.
“People sometimes disparage sleep as ‘lost’ time,” he said. But even if the link between sleep and memory lessens with age, “sleeping well still is linked to better mental health, improved cardiovascular health and fewer, less severe disorders and diseases of many kinds.”
*Study co-author is Donald Bliwise, Ph.D., professor of neurology at Emory University School of Medicine.
ABOUT BAYLOR UNIVERSITY
Baylor University is a private Christian University and a nationally ranked research institution, characterized as having “high research activity” by the Carnegie Foundation for the Advancement of Teaching. The University provides a vibrant campus community for approximately 16,000 students by blending interdisciplinary research with an international reputation for educational excellence and a faculty commitment to teaching and scholarship. Chartered in 1845 by the Republic of Texas through the efforts of Baptist pioneers, Baylor is the oldest continually operating University in Texas. Located in Waco, Baylor welcomes students from all 50 states and more than 80 countries to study a broad range of degrees among its 12 nationally recognized academic divisions. Baylor sponsors 19 varsity athletic teams and is a founding member of the Big 12 Conference.
ABOUT BAYLOR COLLEGE OF ARTS & SCIENCES
The College of Arts & Sciences is Baylor University’s oldest and largest academic division, consisting of 24 academic departments and 13 academic centers and institutes. The more than 5,000 courses taught in the College span topics from art and theatre to religion, philosophy, sociology and the natural sciences. Faculty conduct research around the world, and research on the undergraduate and graduate level is prevalent throughout all disciplines.