Memory remains sharp after 70 years of age if you sleep well in your younger years, says a new study, that was done to determine if sleep and age-related changes are related.
Michael K. Scullin, Ph.D., at Baylor University examined 50 years of sleep research to determine whether improving sleep early in life might delay, or even reverse, age-related changes in memory and thinking, and came across studies that showed that sleeping well in middle age predicted better mental functioning 28 years later.
The article 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.
The article is published in the journal Perspectives on Psychological Science.