We all know sleep is important—and that many of us don’t get enough.

“Sleep is critical in healing, growth and memory consolidation as well as a number of important hormonal processes,” says Steven Y. Park, MD, assistant professor of otolaryngology at Albert Einstein College of Medicine and author of Sleep Interrupted: A Physician Reveals the #1 Reason Why So Many of Us Are Sick and Tired. “Studies show that getting too little sleep (as well as too much sleep) is associated with significantly higher rates of hypertension, diabetes, depression, cancer and death.”

Yet for all the airtime devoted to healthy sleep habits (or lack thereof) there are some surprising facts many people don’t know. For example:

Lack of sleep promotes weight gain. Sleep helps regulate appetite hormones so not getting enough shuteye encourages cravings of sugary, fatty, starchy and/or salty foods. None of which are good when watching the waistline.

The amount of sleep we need can vary greatly between individuals. “This is a function of their specific brain’s needs,” says Dennis Rosen, MD, assistant professor of pediatrics at Harvard Medical School, associate medical director of the Center for Pediatric Sleep Disorders at Children’s Hospital Boston and blogger at Psychology Today’s Sleeping Angels . “Some adults do fine on six hours; others cannot function with fewer than eight-and-a-half. The former are not ‘supermen’ and the latter aren’t lazy—it’s just natural variability.”

Obstructive sleep apnea can cause more than just a bad night’s sleep. If untreated it increases the risk of heart attack or stroke by two to three times. And odds of getting into a car accident? Try a FIFTEEN times greater likelihood.

Obstructive sleep apnea is not always obvious or easy to diagnose. While it often affects people who are older and/or overweight, it can also strike individuals who are young, thin and don’t even snore. In fact, 24 percent of men and 9 percent of women have it (and 64 percent of people over age 65)—yet 80 percent are not diagnosed.

Many people think they wake up at night because they need to go to the bathroom. However, more likely it’s a breathing obstruction that caused the waking. “Going to the bathroom two or more times at night increases your risk of dying by 50 percent,” says Dr. Park.

Shiftwork is also dangerous due to its affect on sleep. In fact, it’s considered a carcinogen along with ultraviolet radiation and diesel fumes.

So how can we know if we’re getting enough quality sleep? Listen to our bodies. For people who don’t feel sleepy during the day and don’t have significant medical, behavioral or psychiatric problems all systems are likely go.

To truly put it to the test, Dr. Rosen suggests the following. “To really answer if you’re getting enough sleep you need to keep careful track of how much you sleep when on vacation, for example, untrammeled by other needs.”

Finally, keep in mind that while obstructive sleep apnea can be serious and should be evaluated by a doctor if suspected, there are things we can do on our own to improve our sleep as well. Keep to a regular sleep schedule (no, that doesn’t mean sleeping until noon on weekends), avoid screen time an hour or two before bed and realize the importance of a good night sleep. “Think of sleep as your most important appointment of the day,” says Dr. Park. “Don’t be late and don’t stand yourself up.”

By Kristen Stewart

Kristen Stewart is a freelance writer specializing in health, nutrition, parenting and lifestyle topics. To learn more, visit her website at www.kristenestewart.com.