Lights out and technology on? Finishing up that last report for work, Facebooking with our friends, binge-watching Game of Thrones—there are so many options to occupy and entertain us late into the night. But our new nocturnal habits aren’t just making us a nation of sleepy people; they’re hurting our health in more ways than you may realize.
Teresa Hesley is a sleep cheater. A working mother with two young children, often the only occasion Hesley gets to spend one-on-one time with her husband is at night after the kids have gone to bed. “That’s basically our time together,” says Hesley, a 33-year-old statistician who works for the U.S. Bureau of Labor Statistics. “A lot of times we’ll just watch TV, or we’ll talk for a while. Just relaxing and not going next-to-next-to-next. We’ll end up pushing that.”
Her 10 p.m. bedtime sounds OK. The problem is that, on most days, her alarm clock goes off at 4:20 in the morning so she can catch the 5:12 train from Arbutus, Maryland, to Washington, D.C., where she works. Her packed week includes a graduate course in statistics and two nights of recreational volleyball. “It kind of has a cumulative effect through the week,” Hesley says. “Monday, I’m a little sluggish, just because it’s Monday. By Wednesday, I’m like, Oh man . . .”
Hesley isn’t alone—we’re a nation of sleep cheaters. According to the Centers for Disease Control and Prevention, roughly 41 million working adults say they get six or fewer hours of sleep each day. Everyone is different, but most people need between 7.5 and 8.5 hours of sleep a night.
What causes us to cheat on sleep? Perhaps the better question nowadays is, what doesn’t? Squeaking in work once the kids are in bed. Answering those last personal emails. Maybe there’s that final run of laundry spinning. And after all of it, when we’re truly exhausted, we collapse on the sofa to fiddle with our smartphones or catch up on the latest Netflix series. Soon, it’s way too late—already?—and the alarm clock is poised to squawk in just a few hours, beckoning us back awake and back to work.
It’s not just that our habits are creating a vast army of cranky individuals; we’re also putting ourselves at risk for a host of health issues. Lack of sleep can affect our cognitive abilities, mood, and ability to deal with pain and metabolize food, among other things.
“There are so many other distractions, we really see sleep as sort of this luxury item,” says neurologist Charlene Gamaldo, medical director of the Johns Hopkins Center for Sleep at Howard County General Hospital and an associate professor of neurology at the Johns Hopkins School of Medicine. Even Gamaldo admits to cheating sleep: She gets about six to seven hours per night. “There are 24 hours in a day; that’s never going to change,” she says. “But what’s being robbed is our health—our sleep.”
“There are so many other distractions, we really see sleep as sort of this luxury item.”
Although sleep medicine is a growing field of study, there’s a lot we are still trying to understand about sleep—including why we even do it in the first place. Researchers do know, however, that not getting enough shut-eye affects our health.
“Sleep really impacts pretty much every physiologic function that you have, both your brain and how your body and organs perform,” says sleep researcher Michael Smith, a psychologist who directs the Johns Hopkins Center for Behavior and Health and co-directs the Johns Hopkins Center for Sleep-Related Symptom Science. During sleep, he explains, “the space between the cells in your brain actually expands and allows fluid to flow through and wipe away the detritus of the day—all the toxins, in a sense, that your brain puts out.”
The funny thing about cheating on sleep in order to get more things done during the day is that it’s actually counter-productive. When we’re sleep-deprived, our minds operate less efficiently. Research has shown we’re less able to concentrate or to quickly recall information like a person’s name, and our brains have a tougher time retaining and retrieving memories.
You say this doesn’t sound like you? Perhaps that’s because people are, in fact, poor judges of how badly sleep-deprived they are. One University of Pennsylvania study published in 2003 found that by the end of a two-week study—when “performance was at its worst levels” on tests like matching up numbers with symbols—people getting four to six hours of sleep a night said they felt “only slightly sleepy.”
It’s possible to get away with some level of sleep deprivation because we seem to be able to compensate when it comes to logical tasks and even some complicated, rule-based tasks. But try to think creatively or innovatively, or to deal effectively with the unexpected, and results are not so good. This is particularly problematic when a person’s profession requires analysis and critical thinking. Take the practicing physician, says Gamaldo. “When we see a patient, it’s not like the patient goes, ‘This is what’s going on, and I’m going to give you some options for what it is.’ No, you have to take all that information, process it, retrieve from your knowledge and experience, and then spit out something.”
What’s more, sleep deprivation affects your prefrontal cortex, the area of your brain that deals in part with complex emotion and impulse control. That prefrontal cortex is critical when it comes to moderating the amygdala, the area of the brain that processes emotions and memories. So a lack of sleep can make us anxious and emotionally unstable. Serious sleep issues, like chronic insomnia, can lead to depression.
“The amygdala is specifically activated by either positive or negative emotional things,” explains Gamaldo. “The prefrontal lobe helps to sort of neutralize or balance it. I like to tell folks who are Freudians: Your amygdala is your emotional brain, or the id part of your personality. The prefrontal lobe is like the super ego that says: ‘Let’s think about this rationally.’” With sleep deprivation, however, that connection between the prefrontal cortex and the amygdala is affected. The cortex is less able to blunt negatively charged situations and emotions, meaning it’s more difficult to rationalize them. Think road rage, says Gamaldo.
Speaking of driving, the National Transportation Safety Board equates fatigue-impaired performance to alcohol-impaired performance. It cites a 2003 study published by Henry Ford Hospital’s Sleep Disorders Center in Detroit that found that losing two hours of sleep was similar to blowing a .05 percent on a breathalyzer. The AAA Foundation for Traffic Safety has estimated that nearly 17 percent of fatal car crashes studied in a nationally representative sample of accidents involved—though were not necessarily caused by—a sleepy driver. Fatigue has also played a role in numerous plane crashes. There are now rules regulating the number of hours airline pilots and commercial drivers must rest before going to work.
Michael Smith has been working in the field of sleep research for nearly 20 years. He’s an expert on the neurobehavioral causes, consequences, and treatments of sleep loss and on how the latter relates to pain. His research has shown that various types of sleep deprivation—from missing out on a few hours to chronic insomnia can amplify a person’s pain and may even be a risk factor for developing pain that stretches out longer than the normal healing period.
Currently, he’s investigating the mechanisms by which sleep deprivation amplifies pain. One study involves disrupting the sleep of healthy people so that they get about four hours of sleep a night for two to three nights in a row. “One of the theories is that sleep deprivation causes inflammation,” says Smith. “And we know inflammation sensitizes your nociceptors, the neurons that fire your pain signals. So if sleep deprivation exacerbates or creates inflammation, then that might be one way it makes us more pain sensitive.”
In a separate study, Smith found that disrupted sleep might contribute even more to our sensitivity to discomfort. Women who experienced four hours of sleep with forced awakenings suffered an increase in spontaneous pain compared to women who simply slept for four hours. “This means that it’s not just the amount of sleep loss; we found that it was particularly bad if you’ve had this fragmented sleep,” says Smith.
Smith believes this may be a sign that sleep disruptions weaken our body’s natural pain regulating system, which functions in part by endogenous opioids, like endorphins. These chemicals are similar to morphine and relieve pain and provide pleasant feelings. (In turn, this may also mean that pain relief drugs like morphine may be less effective on sleep-deprived hospital patients.) “We are investigating whether sleep deprivation may down-regulate your ability to modulate pain using the opioid system,” he says.
Sleep deprivation affects your prefrontal cortex, the area of your brain that deals in part with complex emotion and impulse control.
As if being fuzzy-headed, emotionally vulnerable, and sensitive to pain isn’t enough, it also seems that sleep deprivation can hit us around the waistline. Recent research has shown that not only do we crave calorie-dense foods when we’re sleep-deprived, we’re also less capable of fending off our amygdala’s instant gratification urge to chow down, damn the calories! Hormones that help manage our appetite—leptin and ghrelin—end up working against us. Naturally occurring levels of the former, an appetite suppressant, and the latter, a hunger stimulant, can be thrown off-kilter when we don’t sleep, causing us to eat more.
What about the argument that if you’re up late, your body needs extra calories to keep going? That’s true, but we still may be eating more than our body needs.
Last year, a study out of the University of Colorado Boulder found that people who slept only five hours burned 5 percent more energy than test subjects who slept up to nine hours. However, they consumed 6 percent more calories—gobbling up more calories in after-supper snacks than at any of their individual meals. After five days, the short sleepers had gained almost two pounds.
“[Sleep deprivation] also affects things like our metabolism [and] the way we process and handle sugar,” says Smith. “If you sleep deprive yourself even for four hours [a night] for about a week, you’ll get insulin resistance, which is a main feature of type 2 diabetes.”
Some of the most dramatic effects of fatigue occur in people who are chronically sleep-deprived, like shift workers. According to the Bureau of Labor Statistics, nearly 15 million Americans work at jobs with irregular schedules, like night shifts or rotating shifts. “There’s data that their life span is shorter,” says Gamaldo. Shift workers are at a potentially increased risk for colorectal cancer and gastrointestinal disorders. And although more research is needed, several studies have linked a higher risk of breast cancer with women who work mostly at night, like some nurses.
“It’s not just the amount of sleep loss; we found that it was particularly bad if you’ve had this fragmented sleep.”
Scientists believe that being constantly exposed to light at night may be one of the possible culprits; this exposure can disrupt our body’s melatonin, an anticarcinogenic hormone produced by our brain’s pineal gland that is secreted when it’s time to sleep. Johns Hopkins biologist Samer Hattar is one of those scientists concerned about nighttime light. While his research does not involve sleep deprivation per se, it nevertheless provides more reason to switch the lights off at a reasonable hour.
Hattar studies mice and their circadian clocks, the biological timekeeper that runs in all of us on a roughly 24-hour cycle tied to environmental light. In many ways, we are governed by these clocks—they dictate everything from our hormones to sleep and hunger cycles. Despite all the arti-ficial light that surrounds us, these clocks are still most influenced by the sun.
Hattar and his lab have found that even abnormal exposure to light at night that doesn’t affect mice’s sleep patterns can still affect their mood and cognitive abilities. Mice on a cycle that alternated between light and darkness every three hours—a cycle used because it did not affect their circadian clocks—exhibited signs of depression and learning problems. “One of the things that excites me is that since light has such a major effect on us, does this irregular light schedule we are exposing ourselves to underlie a risk factor for neuropsychological diseases?” says Hattar. “Like depression or autism, we know these diseases have genetic susceptibility factors. Maybe these, under very defined light-dark environments and sleep-wake cycles, can be subdued and not as expressed as would happen if you put them under irregular light conditions.”
Hattar is hoping to investigate this theory further. His findings in mice, however, are cause for concern for more than just shift workers. With our fondness for squeezing in a few more minutes with tablets, televisions, and smartphones, we often forget that we’re getting more than just entertainment and information in the evening. We’re also getting a dose of artificial light that can help cheat us of sleep.
“You don’t want to be active 24 hours a day, and you don’t want to get light 24 hours a day,” says Hattar. “Light, like everything else, has a temporal domain to it.”