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While your brain is busy repairing and strengthening itself, your body follows suit—your immune system tends to be most active when you’re sleeping. For example, if you’ve just gotten a shot at the doctor’s office, try to make time to sleep that same night. Vaccinations “take” better with a full night’s sleep: Your well-rested body will make more antibodies designed to attack the bug you got vaccinated against, leaving you better able to fight off infection. Sleep deprivation, on the other hand, is tough on your immune system, making you more susceptible to infection. In fact, sleep is so important for immunity that your immune system can trick you into sleeping more so it can fight off infections: Cytokines, defense chemicals your body release as part of an immune attack against invaders, make you sleepy—which may help explain why you need so much sleep when you’re sick.

Scientists are also uncovering more evidence that sleep is crucial for maintaining a healthy weight. This isn’t just because midnight snacks tend to be calorie-heavy favorites like leftover pizza or ice cream; hormones that govern hunger fluctuate with sleep. Sleep deprivation increases your levels of ghrelin, a hunger-stimulating hormone, while decreasing your levels of leptin, a hunger-suppressing hormone. This may cause you to over-eat if you haven’t been sleeping enough. Researchers have found that sleep-deprived people eat more than those who are well-rested, but don’t move enough to make up for the extra calories. As a result, many scientists are beginning to think that sleep deprivation contributes to obesity.

And sleep doesn’t just keep your hunger in check: There’s evidence that sleep helps regulate your blood sugar—and that sleep deprivation might increase your risk for type 2 diabetes, a disease in which blood sugar spirals out of control. A study of extreme sleep deprivation found that volunteers kept awake for one or more nights showed various signs of pre-diabetes, a condition that usually leads to type 2 diabetes if left untreated. Another study that limited volunteers to four hours of sleep a night for four nights found that their ability to respond to insulin, a hormone that keeps blood sugar at healthy levels, dropped by 16 percent.

Still not convinced that a good night’s sleep is key to your health? Researchers from the UK analyzed the results of 17 sleep studies that altogether included more than 1.3 million subjects. They found that people who are chronically sleep deprived are more likely to have cardiovascular disease, type 2 diabetes, hypertension, respiratory disorders, and are more likely to be obese. Considering the litany of problems with sleep deprivation, it may come as no surprise that the study found that people who sleep seven to eight hours a night have the longest lifespans; by comparison, those who sleep less than seven hours a night have a 12 percent increase in mortality.

Don’t Cheat on Sleep

If you can only drag yourself out of bed after swatting your snooze button a few times, you’re not alone. Sleep deprivation is all too common in modern society, says Dr. Claman. On average, Americans today sleep about an hour less per night than people did a hundred years ago—likely a result of taxing work schedules and electronic gadgets that distract you from going to bed.

So how do you get a good night’s sleep? Make your slumber a priority and aim for seven to nine hours a night. Set up (and stick to!) a regular sleep schedule: Try to fall asleep and wake up around the same time every day. These secrets to a better night’s sleep can help you establish a nighttime routine.

One important tip to remember in the digital age: Turn off electronics and other bright lights before bed.

“Electronics disturb sleep for two reasons,” says Jamie Zeitzer, PhD, who studies sleep rhythms as an assistant professor at Stanford University. The first is psychological: It’s tough to unwind if your mind is mulling over your to-do list. “Checking email late at night makes you preoccupied with work,” Zeitzer says—a recipe for insomnia. Second, the light emitted from your TV screen or smartphone may wreak havoc on your internal clock, which governs your feelings of wakefulness and fatigue. This clock is responsive to light levels; when it’s dark out, your body secretes the hormone melatonin to make you feel drowsy. But your clock can be fooled by your electronic devices.

“Depending on what device you’re using and how close it is, light at night of sufficient intensity can shift your circadian rhythm a time zone or two away,” says Dr. Zeitzer. So the light from that glowing computer screen may trick your body into thinking it’s earlier than it is—keeping you awake late into the night. As a result, sleep experts recommend spending the last hour of your day in low light to lull your body to sleep, and then kick-starting your morning with bright lights to help your internal clock wake you up.

As for those inevitable days when you just don’t get enough shut-eye, Dr. Claman cautions against trying to make up for missed sleep with marathon sleeping sessions later on; remember, even if you have the luxury of being able to sleep until 2pm on the weekends, it won’t erase the sleep debt you’ve accumulated. Instead, try a nap. Naps lasting about 1.5 to 2 hours allow you to go through a full sleep cycle and can make up for sleep you might have lost during the night. If you need a quick boost, try taking a 20 to 40 minute power nap during the day. After, you should find it easier to concentrate and stay alert. However, make sure to time it right—taking a nap too late in the afternoon might make it more difficult to fall asleep at night.

Remember: From weight and immunity to attention and memory, sleep has a huge impact on your wellbeing. So if you’re looking for an easy way to learn, heal, ward off disease and stay slim, do yourself a favor: take the time to get a good night’s sleep. 

Published December 4, 2012. 

Margot Hedlin is a science and health writer living in San Francisco.

See also:

• Secrets to a better night's sleep
• Track your Zzzzz's with our free tool!
• 16 ways to get all-day energy