But sleep isn’t just a cozy reward after a long day—and it’s certainly not a sign of laziness or weakness. Sufficient sleep—which for adults is defined as getting at least seven hours per night by the CDC—is an absolutely vital driver of every physiological system in the human body. When we’re sleep deprived—which more than one third of adults are—our health and wellbeing can suffer in myriad ways: mental, physical, and emotional. You don’t need to have pulled an all-nighter, or find yourself falling asleep mid-sentence, to be considered technically sleep deprived. In fact, you may not even realize you’re not getting enough sleep, because you might not feel particularly tired. There are many less obvious signs of sleep deprivation that go beyond yawning, nodding off at your desk, or having heavy eyelids. But getting less than seven hours of sleep a night is all it takes, and the effects are subtle, but cumulative. In his book Why We Sleep: Unlocking the Power of Sleep and Dreams, professor and director of UC Berkeley’s Sleep and Neuroimaging Lab, Matthew Walker, PhD, describes scientific research that concludes: sleeping for only six hours a night for 10 days can make you as impaired as someone who’s been awake for 24 consecutive hours. To avoid long-term health issues and improve your day-to-day life, here’s how to identify seven sneaky signs of sleep deprivation. RELATED: Here’s How to Manage Stress So You Feel in Control In a wide range of sleep studies dating back almost 40 years, Robert Stickgold, PhD, director of the Center for Sleep and Cognition at Harvard Medical School, has discovered that nighttime sleep and dreaming promote new learning, memory consolidation, and greater creativity. Lately, however, Stickgold has also shown in newer experiments that daytime naps may do as much good for memory processing as a full night’s sleep. Naps even seem to trump coffee as a workday boost (although drinking a cup of coffee before taking a nap is known to be the ultimate pick-me-up combo). Caffeine does boost cognitive power for up to a half hour, “but sleep actually takes the recent information you’ve learned and files it away so you can more effectively take in new information,” Stickgold told Time magazine. More recently, researchers have identified a strong connection between lack of sleep and increased risk for developing Type 2 diabetes, a metabolic disorder frequently triggered by overeating and obesity.This prompted the medical journal Lancet to argue that, given the “24/7 lifestyle of modern societies,” doctors everywhere should work harder to “motivate their patients to enjoy sufficient sleep” as a way to prevent—and treat—both obesity and diabetes.
