THE DETAILS: In the study, 33 adults aged 67 on average, and 29 adults aged 27 on average, stayed overnight in a sleep lab run by sleep expert Sean P. Drummond, PhD, and colleagues at the University of California–San Diego. The researchers measured the sleep duration and quality for each subject, then tested everyone the next day on a variety of brain-activity, learning, and memory tests.
Among the older group, the absolute minutes of sleep they got had the most influence on their cognitive tests, says Drummond. For example, those who got more sleep time—regardless of its quality—were able to remember a list of random nouns better than those who slept for shorter periods. By contrast, with the younger group, individuals who managed to sleep in quality, deep-sleep chunks scored better on the cognition tests than those who got less quality-sleep time. Total sleep time had no bearing.
Read on for advice about getting the sleep you need.
WHAT IT MEANS: The connection between sleep and brain function has been well established for years, but this study points more specifically to the type of sleep that may be key, at least in the short-term (subjects were tested after just one night of sleep observation).
So if you've got a daunting intellectual or emotional task on a given day, knowing whether it's more time sleeping or better quality sleep that's best for your age group might help you the night before. But for overall health, we all need to go for both and treat sleep with the respect it deserves, says sleep expert Jeanne Duffy, MBA, PhD, of the Harvard Medical School’s Division of Sleep Medicine. “No matter your age, all the usual sleep tips are valid and important, such as creating a cool, quiet, comfortable bedroom environment and not taking caffeine close to bedtime,” says Duffy. “But the bigger point is to remember how vitally important sleep is for good health and top performance—both physically and mentally.”
Here's what you should keep in mind when considering how much sleep you need (or how much you're not getting):
• You underestimate your need for sleep. Think you're getting enough sleep? Think again. “In sleep-deprivation studies, after three or four days people generally stop reporting feelings of sleepiness, yet they continue to do worse and worse on cognitive tests without even realizing it," says Duffy. If you're one of those people who says, ‘Oh, I don’t need much sleep. I’m fine with five or six hours a night,’ there's a good chance you're not so fine—you're cognitively impaired. You just don’t know it. (Because you're cognitively impaired.) One classic test: If sitting in a dark room during the day makes you start to nod off, you're not getting enough sleep.
• Sleep helps you remember things. If you skimp on sleep because you need the time to get more things done, you may in fact be losing time because your brain's not working at full capacity. "We’ve found that adequate sleep not only helps you learn something new—you process it better, and take it in more clearly—but you also do a better job of consolidating that information and putting it into the proper memory banks," says Duffy. Therefore you retain it better.” One recent study found that taking naps can help boost your brainpower.
• Try getting more than eight. “Humans actually need about 8½ to nine hours of sleep a night to be at their best," says Duffy. Unfortunately, almost no one gets that. Which means that pretty much all of us are walking around cognitively impaired.” To step out of the zombie parade, see our stories on learning sleep skills and avoiding sleep deprivation.