Our bodies give us plenty of signals when we’re tired. But some of us are so used to being sleep deprived that we remain oblivious to how impaired we really are. Sleep debt isn’t something you can pay off in a weekend, researchers say—it can take weeks of building up restorative sleep habits. Here are some signs you may need to make sleep a more urgent priority.
Simple decisions stump you
You’re up late one night booking your next vacation, and even though you know the dates and destination, you’re overwhelmed by minor details. Should you get a refundable ticket? Window or aisle seat? Rent a car now or later? When you’re tired, you’re less able to distinguish between important and irrelevant information, such as your seat assignment, according to Sean Drummond, PhD, a sleep researcher at the University of California, San Diego. The result: Even the simplest decision takes on exaggerated importance.
Tired people also take riskier gambles to maximize results (Maybe if I wait until the last minute, the ticket price will go down) and have trouble adjusting to changing circumstances (like firming up an itinerary if flying from an unfamiliar airport).
You’re still hungry—after eating all day
Shortchanging your nightly sleep can make your waistline suffer. Studies show that chronic sleep loss can disrupt blood sugar levels and cause the body to produce less leptin, a hormone that curbs appetite, and more ghrelin, leptin’s hunger-stimulating counterpart. Because of these physiological changes, you may be more likely to overeat when you skimp on sleep—and the food you pick probably won’t be either nutritious or a lasting source of energy.
Tired people tend to be particularly drawn to sugars and other simple carbohydrates, probably because the body is looking for a quick pick-me-up, says Lisa Shives, MD, a spokesperson for the American Academy of Sleep Medicine. Sleep deprivation also tends to erode self-control, making you more likely to choose a brownie over carrot sticks.
You keep coming down with colds
Inadequate sleep can leave you more vulnerable to infection than those who are well rested. In one study, researchers injected healthy volunteers with a cold virus. Those who slept less than 7 hours a night for the previous week were 3 times more likely to develop symptoms than those who got 8 hours or more. In another study, people who got only 4 hours of sleep for several nights in a row had a weaker immune response to the flu vaccine than those who slept between 7.5 and 8.5 hours.
Weird things make you cry
Do those ballads on American Idol move you to tears? Try going to bed earlier. Don’t automatically chalk up your sudden weepiness to PMS: Without sleep, you are more emotionally volatile. In one brain-imaging study, for example, people who missed a night of sleep and viewed disturbing images had 60% more activity in the amygdala, which is involved in processing fear and anxiety, compared with better-rested volunteers. The study also found that the sleepy volunteers’ amygdalae communicated less with the part of the brain that determines appropriate emotional responses, suggesting that they weren’t doing a good job of tempering their emotions.
When we’re sleep deprived, we may also feel glum because tired brains store negative memories more effectively than positive or neutral ones. As a result of all this, Shives says, “if you are chronically sleep deprived, you could act like someone with depression.”
You’ve become a klutz
One moment you’re pouring yourself a bowl of cereal and the next thing you know, you’ve spilled it all over your newly cleaned floors.
Sound familiar? Researchers have accumulated ample evidence that the sleep deprived have slower and less precise motor skills, but exactly why isn’t yet known, says Clete Kushida, MD, PhD, director of Stanford University Center for Human Sleep Research. Sleepy people may be clumsier for several reasons: Impaired reflexes and a lack of focus may make it hard for them to react quickly enough to things that spring up in their path.
Another possibility: Sleepiness throws off balance or depth perception. In any case, it’s not uncommon for very sleepy people to black out momentarily when the body’s urge to sleep gets too strong. So it’s possible that your klutziness stems from “microsleeps” that last for a second or two, Kushida says—just long enough to trip on the curb or drop a glass.