Now a study done in Sweden has shown something new: Losing a half night of sleep—and then being put under mental stress—can hinder our retrieval of stored memories.
It’s a situation that “can possibly be detrimental in real-world scenarios,” said the study’s lead author, Jonathan Cedernaes, MD, PhD, in a statement. He is a neuroscience researcher at Uppsala University in Sweden.
Put another way, the researchers found that getting a full night’s sleep not only helps memories form in the brain but also gives us access to those memories during stressful situations.
The upshot, Dr. Cedernaes said, is that people who are regularly short on sleep “may improve their academic and occupational performance … under stressful conditions” by increasing their “snooze time.”
The stress factor
The Swedish study sheds new light on how memories are processed during sleep, according to Jason Coles, MD, a sleep medicine specialist who works with adult patients at the Spectrum Health Sleep Disorders Center and pediatric patients at Spectrum Health Helen DeVos Children’s Hospital.
“Previous studies seemed to show that the most important part of the sleep (for memory formation) is the deep sleep … and most of that happens in the first half of the night,” Dr. Coles said.
“So prior to this study, (sleep experts) thought that four hours was just as good as eight hours as far as being able to recall the data that you learned the previous day.”
Adding stress put a different spin on things.
Working with a group of healthy young men, researchers had some participants sleep four hours and others sleep eight hours. In the morning, all of them were tested on data presented the day before. Then they were exposed to a stressful situation and tested again.
For those who’d had a full night’s sleep, the stress had no effect on their test performance. But those who’d had a short night of sleep did worse on the test after facing mental stress.
The biggest surprise here, Dr. Coles said, is that our memory function relies on more than just the deep sleep of the first half of the night. “The second half of the night—where we’re in the REM sleep and the more shallow stages of sleep—seemed to have some additional benefit that kind of protects you against the negative effects of the stress.”
The research reinforces the notion that we need to get enough sleep if we want to do our best work.
Case in point: students
The study could have relevance for college and high school students, who often stay up late studying and don’t get enough sleep, Dr. Coles said. “You think about college and high school being stressful periods of your life, too, and it just reinforces the need to get enough sleep every night to be able to do your best on tests and for learning.”
This could be especially true for students who find test taking itself to be stressful.
So what can we do to encourage good sleep habits? Dr. Coles offers a few ideas.
Expert tips for healthy sleep:
- Get enough sleep each night. The optimal amount isn’t the same for everyone, but adults generally need between seven and nine hours of sleep for top cognitive ability. Another way to looking at it, Dr. Coles said, is to “know how much sleep you need to feel rested when you get up, and try to get at least that much.”
- Stick with a regular schedule—awake during the day, asleep at night. “The body has a process called the circadian rhythm, which tells us what time of day to be most alert and awake. … If you’re trying to be awake at the time of day when your body’s actually telling you to be sleepy, that throws off your functioning,” Dr. Coles said. Keeping to a regular rhythm helps you to focus and do your best during the day.
- Create a healthy environment for sleep by keeping the room cool, quiet and dark. This includes removing TVs, computers, tablets and chirping cell phones from the bedroom.
- Avoid caffeine and alcohol in the evening. Alcohol “tends to help you to fall asleep quicker, but it also tends to wake you up more throughout the night,” Dr. Coles said.
- If you have trouble falling asleep, let yourself unwind. Choose relaxing activities for the hour before bedtime to give yourself a winding-down period.