Scientists are learning more ans more about what, exactly, sleep is good for. It’s healthy, for one thing: people who experience chronic sleep deprivation, regularly getting too little sleep, are prone to a number of problems, including diabetes, depression, cardiovascular disease, even weight gain. A wakefulness binge, a single incident of not sleeping, can cause problems as well; not sleeping for days on end can be harmful or even fatal. Sleep is also when the brain goes through its self-cleaning cycle, flushing out cellular waste products generated by ordinary brain activity so they don’t damage cells.
That’s why it’s important to get enough sleep—seven to eight hours each night, according to experts. When someone doesn’t get enough sleep, they accumulate sleep debt, and sleep debt, like any debt, comes with interest. That’s because it’s not enough to average seven hours a night; the cleaning process takes time. In one study, people who slept six hours a night for ten nights showed the same degradation in performance as people who had gone just one night without any sleep at all. Someone who is chronically sleep-deprived and gets one good long night is only back to normal for about six hours the next day. After that, the lack of focus, inattentiveness, and poor memory come back. That means the all-too-common pattern of short nights during the week and sleeping in on weekends isn’t actually a successful sleep strategy.
There is some good news. While it’s not always possible to get enough sleep to make good the debt, subjects in a study who had been made to believe they’d had exceptionally restful sleep were actually better rested than people who’d been told they’d slept poorly. The difference didn’t show up in all the measures used in the study, but the researchers did see a clear difference. However, even convincing yourself you slept well can only go so far.
To really get a good night’s sleep, look at the venue. A dark, cool room with as few distractions as possible is the optimal environment. At the very least, the sleep space and the serious activity space—a home office, for example, or the computer desk—should be distinct and quite separate. Exercise at night isn’t as disruptive to sleep as once believed, but caffeine and afternoon naps are; both should be avoided within six hours of bedtime.