Think you can learn to survive on less than six hours of sleep a night? Think again. Adults typically need between seven and nine hours of shut-eye a night to function at their best. Between health care expenses and lost productivity, insufficient sleep in the U.S. rings in at an annual cost of about $66 billion.
How come? When you’re awake, a chemical called adenosine builds up in your blood, and when you sleep, your body breaks it down. Skimp on sleep, however, and adenosine builds up in your bloodstream, making you more and more desperate to snooze. Your reaction time slows, which makes you more prone to dangerous mistakes when driving. A shortage of sleep is to blame for some 100,000 traffic accidents, 76,000 injuries, and 1,500 deaths a year.
And it adds up. Getting just two to three hours too little sleep for a few nights can have the same effect as pulling an all-nighter—yet it’s something that many Americans routinely do. If that doesn’t sound like a big deal, consider this: Staying up for 24 hours straight and then getting behind the wheel is like driving with a blood-alcohol content that deems you legally drunk in all 50 states.
Just like with a credit card or a mortgage, sleep debt eventually has to be repaid. And the more you add to it, the bigger your balance. Sleeping in on the weekends (a common practice) is one way that you might try to combat a shortage of weeknight sleep, but it’s usually not the best strategy. If you have to overcome a one- or two-hour sleep debt, it might work. But if you’re under-sleeping by, say, an hour every night, Monday through Friday, you’ll end up with a whopping five hours of sleep debt by the time Saturday rolls around. And sleeping in too much on Saturdays and Sundays can make things worse by throwing off your regular snooze schedule and making it harder to sleep on Sunday night.
When it comes to paying down sleep debt, slow and steady is the way to go. Start by cleaning up your sleep hygiene habits to maximize the hours of snooze time that you get during the week. Even going to bed just 15 minutes earlier each night may help. Stick to a regular sleep and wake schedule, avoid caffeine and alcohol, exercise daily, and relax before bed with a hot bath or a good book instead of electronics (which can disrupt sleep). A daytime nap may also help you catch up, if it’s possible for you to take one regularly.