In a nation chronically wanting for rest, the gravest danger is not merely the molecular impact of sleep deprivation—but the simple fact that we no longer realize just how tired we are.
By Mark Wolverton published September 2, 2013 - last reviewed on June 9, 2016
It was supposed to be another routine trip for the venerable Staten Island Ferry. Instead, the afternoon crossing on October 15, 2003, led to one of the worst transportation disasters in New York City history. At about 3:30 p.m.,as the ferry Andrew J. Barberi came in for docking at the St. George terminal, it crashed into a concrete pier at full speed, killing 10 people and injuring 70 more. The subsequent investigation by the National Transportation Safety Board found that the main cause of the accident was the "unexplained incapacitation" of the assistant captain—exhausted, he'd passed out at the boat's controls.
It was a tragic outcome for a common phenomenon: experiencing fatigue behind the wheel. In a recent AAA Foundation for Traffic Safety survey, over 40 percent of respondents reported having "fallen asleep or nodded off" while driving at least once; more than a quarter admitted to having driven while "so sleepy [they] had a hard time keeping [their] eyes open" within the past month. Studies by the Centers for Disease Control, NTSB, and other agencies estimate that drowsy driving may play a part in up to 6,000 fatal auto accidents annually. Those annoying "rumble strips" along the road's shoulder are there for good reason.
A 2011 CDC analysis found that over 35 percent of adults routinely get less than seven hours of shuteye nightly. There's no magic number for the perfect amount of sleep, but research suggests that most of us require more—about eight hours—to perform optimally. (Still, a small percentage of people experience no adverse effects on performance with just five hours.) Unfortunately, societal exigencies such as overstuffed work schedules, family stress, and our constantly pinging smart phones conspire against our getting enough sleep.
Our need for sleep "is fairly inflexible,yet modern social and economic systems provoke it constantly," contends David Dinges, who heads the Sleep and Chronobiology laboratory at the University of Pennsylvania. Rest is too often treated as a disposable option: "It's a badge of courage to stay up all night to get the job done—we celebrate that in our society," says Mark R. Rosekind, who studies issues of fatigue and safety at the NTSB.
As a result, everyday sleep deprivation causes cognitive impairments that lead to minor and major disasters in nearly every occupation: truckers falling asleep on highways, doctors making errors in treatment, nuclear power plant operators missing alarms. New research reveals that sleep loss affects the body on a systemic level as well, creating metabolic and immune disruptions that can cause obesity, heart disease, reduced fertility—even cancer.
Fortunately, while studies increasingly underscore the problematic nature of our national sleep debt, a new science of sleep suggests critical steps we can take as individuals and a society to achieve that elusive, all-important shut-eye.
The Broken Cycle
For over a decade, insufficient sleep has been well established as a health-risk factor: A seminal 2002 study revealed a strong relationship between an individual's reported sleep and mortality. "People who slept less than seven hours a night—or more than nine—were at increased risk for all-cause mortality," says University of Pittsburgh psychiatrist Martica Hall. Other studies revealed a similar curvilinear relationship between sleep duration and conditions such as cardiovascular disease and obesity, although it remains relatively unclear just how disturbed sleep affects our health.
New research suggests that the answer is connected to the functioning of our circadian clock, which evolved to follow the roughly 24-hour light-and-dark cycle of the Earth's daily rotation. The existence of the body's "master clock," the suprachiasmatic nucleus (SCN) located in the hypothalamus, has been known for decades. But only recently have molecular biology and genetics yielded the startling finding that "circadian regulation exists in every cell of the body—the liver, the kidneys, even skin fibroblasts," Dinges says. "It's coordinated and entrained internally, and then entrains to the outside world."
Some researchers compare the system to an orchestra, in which the SCN is the conductor and the other body clocks are the players. The clocks operate all the way down to the genetic level." A decade ago scientists estimated that about 10 percent of genes in the body were under clock control," notes John Hogenesch of the University of Pennsylvania. "Now we're finding that over a third of your genome—including more than half of all drug response pathways—are." If these genetic clocks fall out of sync with the master clock in the SCN, vital processes can be affected—and one way for that to happen is the disruption of overall circadian rhythm by not getting enough sleep.
Research from the University of Surrey published earlier this year helps explain how insufficient sleep alters gene expression—offering important clues to the ways in which sleep and health are linked at the molecular level. The study authors found that after a single week of insufficient sleep (fewer than six hours nightly) blood samples from participants revealed altered activity in over 700 genes—including those related to heart disease, diabetes, metabolism, and inflammatory, immune, and stress responses. While the activity of some genes ceased to cycle in a circadian pattern, other genes' activity, which doesn't typically follow a daily rhythm, began doing so.
A Drowsy Mind
Night by sleepless night, we undermine our cognitive functioning, yet the true extent of our cognitive shortcoming goes largely undetected—except by the scientists who study sleep loss.
In 2003, a team including Dinges, lead by his then colleague at Penn, Hans Van Dongen, conducted a major experiment in which participants were divided into three separate groups: one that slept four hours a night, one for six hours, and a control group for eight hours. The study went on for two weeks and each day participants were repeatedly given a memory test and a psychomotor vigilance task, a simple computer-based assessment of attentiveness and response.
Developed by Dinges, the PVT is simplicity itself: Subjects sit for 10 minutes in front of a screen, hitting a button whenever a bright spot appears; meanwhile, reaction times and other sleepiness indicators (such as droopy eyelids) are monitored. The test measures precisely the sort of cognitive and physiological abilities that insufficient sleep dulls or eliminates. A mere half-second delay in response indicates a lapse of wakefulness—or as researchers term it, "microsleep."
As might be expected, eight-hour sleepers showed no impairment of functioning on the tests. But those getting less sleep did—and performance declined steadily over time, even though participants were getting consistent, if limited, sleep each night. By the study's end, even the performance of the six-hour sleepers had deteriorated as much as if they had been up for 24 hours straight. (A similar study at the Walter Reed Army Institute of Research found that the performance of seven-hour sleepers declined markedly over time as well.)
Yet amazingly, steadily deteriorating alertness was barely reflected in the participants' subjective feelings of sleepiness." By the end of the 14 days of sleep restriction, when performance was at its worst, subjects in the [four- and six-hour] sleep period conditions reported feeling only slightly sleepy," the authors wrote. Dinges suggests that those who are chronically sleep deprived may no longer be capable of reliably appraising their own sleepiness—or they simply don't experience levels of sleepiness in any way commensurate with their actual deprivation. The finding "may explain why sleep restriction is widely practiced: People have the subjective impression they have adapted to it because they don't feel particularly sleepy," the study authors theorize.
"People are impaired at much lower levels of sleep deprivation than they realize," the NTSB's Rosekind agrees. Summarizing Van Dongen's research and other related findings, he notes: "Getting two hours less sleep than you need is enough to impair you and get you into a car crash. You may think you're okay, but if we were to actually measure your performance or alertness, it could be horrible."
The lack of self-awareness about sleep loss is particularly alarming given that deprivation affects high-level cognitive functioning. Over a decade ago, U.K. researchers Yvonne Harrison and James Horne reviewed multiple studies on the impact of sleep deprivation on decision making and problem solving. They concluded that it can lead to impaired communication, a lack of flexibility and willingness to try alternatives, a reduced ability to innovate, and an inability to deal with rapidly changing situations.
We've all made choices while exhausted that we came to regret once we had the chance to rest and reconsider; fortunately, it's usually not too big a deal. But for those among us operating nuclear power plants, managing others' investments, or performing brain surgery, subjective blindness to the reality of fatigue can have serious consequences, costing money, time, and lives.
Sleeping On Company Time
For modern Americans, the type of work we do—and the increasing hours we've spent doing it since the recession began—is a major reason we're not getting the sleep we need. While some occupations are associated with more sleep loss than others, none is exempt. A recent CDC report noted that about 27 percent of people in the financial and insurance businesses are sleep-deprived, with the figure rising to 42 percent among mine workers. "The challenges of schedules cut across many occupations and industries," confirms Roger Rosa, a researcher at the National Institute for Occupational Safety and Health. Still, he observes, "certain ones seem to be more prone to demanding work schedules."
He singles out manufacturing, which uses a lot of shift work schedules, and anything involving continuous processes, like oil refineries. He also notes that sleep loss is a frequent problem for people in seasonal industries, such as construction. "It's not only night versus day work, it could be long hours that people experience, trying to meet deadlines or take advantage of weather or things like that," he says. "Emergency response is another example where often what needs to get done will take a lot of staff working many hours."
Another career notorious for chronic sleep deprivation is medicine, particularly during residency, when fledgling doctors routinely work up to 28-hour shifts. Last year, a study in the Archives of Surgery found that residents were critically impaired by fatigue during more than a quarter of waking hours—and that, when sleep deprived, they were 22 percent more likely to commit medical errors. Meanwhile, a 2009 JAMA study revealed an increased rate of complications when surgical procedures were performed by physicians who had less than a six-hour window for sleep between their last procedure the day before and the first procedure the next day.
Finally, Rosa notes, transportation also ranks among the most sleep-challenged industries. According to a 2011 Federal Aviation Administration report, overwhelming fatigue from long, irregular hours and a lack of breaks was the chief concern among flight attendants, far outranking other complaints. Furthermore, the long hours, with the sleep that they cost and the exhaustion they engender, have been recognized as a major factor in all sorts of airline accidents for decades.
In the early 1990s, the FAA was thwarted in an attempt to update flight and duty-time regulations. Yet support for change swelled after a 2009 plane crash outside Buffalo, New York, in which 50 people died. A contributing factor in the crash? According to the NTSB: fatigue.
Rest For The Weary
Even if we can't fully overcome the effects of not getting enough shut-eye, it's possible to balance our biology with the demands of our society. The first step is to admit that sleep loss is a problem that must be faced individually and culturally.
Fortunately,there are signs that attitudes about sleep's importance are changing. Last fall, after 22 years, the NTSB removed the problem of fatigue from their Most Wanted list, the result of three federal agencies issuing new hours of service regulations for aviation, rail, and commercial trucking. (One example: Commercial airline rules now require a 10-hour minimum rest period for pilots prior to flight duty—and mandate pilots be given the opportunity to sleep uninterrupted for eight of those hours.) "That's a great example of the cultural change that's starting," Rosekind says. "But at the same time, you can look at those rules and say, 'They didn't totally get it.' For example, these new rules don't apply to cargo pilots. They're not quite there yet."
Similarly, 2011 ushered in revised regulations for medical residents, limiting first-year residents to 16-hour shifts prior to an eight-hour break. Second- and third-year residents may still work up to 28-hour shifts (although they are prohibited from accepting new patients within the last four hours).
The shifting cultural tide may also aid an important group of workers who need to stay alert for long, unpredictable hours under significant amounts of stress: soldiers in combat. Modern warfare and technology have heightened the effects of sleeplessness in the military. Researchers Thomas Balkin, Sharon McBride, and Nancy Wesensten of Walter Reed are currently developing an alertness/performance management system, which includes a wrist actigraph device that monitors the wearer's movements with an accelerometer and displays information on recent sleep history and its implications.
Such a "sleep watch" can provide an individualized picture that allows troops to know when they're fully on the ball and in sync with their natural rhythms, and when it's time to knock off and catch some Zs before a mission. The wrist actigraph is anticipated to become standard gear for soldiers and could probably also eventually be used by truckers, pilots, cops, and doctors—anyone whose work puts them at risk for sleep deprivation.
Meanwhile, the adoption of officially sanctioned nap time at companies such as Zappos, Google, and The Huffington Post may be another early signal of a cultural sea change. Though the idea of allowing workers to snooze on the clock might sound outlandish, there's hard data to back the benefits of the practice. Recalling a pivotal NASA study conducted in collaboration with Dinges, Rosekind describes how "we gave pilots a planned rest period in the cockpit and showed that a 26-minute nap boosts performance 34 percent and alertness 54 percent."
Of course, the recognition that organizations like Google give to the importance of sleep remains a rare perk for employees. Even as research progresses, sleep deprivation will continue to undermine our well-being until policies limiting work hours, allowing for naps (and providing spaces for them), and encouraging flexible work hours become commonplace across industries.
Thomas Edison, the famous workaholic insomniac who did so much to change our relationship with sleep through his creation of the light bulb, once dismissed sleep as "a waste of time." He was wrong: It's essential not only for our personal health and well-being, but for the safety and productivity of everyone else.
Ultimately, we can't change our biology or adjust our need for sleep. We can't abolish the fundamental rhythms of life that have evolved over millions of years. But as we learn more about how they work, we can adapt by modifying our attitudes and enacting regulations and business practices that better mesh with our normal human patterns. That certainly won't eliminate every tragedy like the Staten Island Ferry and Buffalo crashes, but it may ensure that when disasters occur, they won't be due to something as avoidable as missing a few hours of shut-eye.
A Shift In Time
Although the problem of sleep deprivation cuts across all occupations, it's a particular concern for those who work the night shift. "Humans evolved in a world where there wasn't electricity to make shift work possible. We're forcing people to live under conditions that we're not suited for," says Charmane Eastman, director of the biological rhythms research laboratory at Rush University Medical Center. "Even when workers use melatonin or sleeping pills to sleep during the day, they're still going to become sleepy at night because their circadian clock says, 'Okay, it's night.'"
Contrary to popular belief, melatonin isn't required for sleep, though it definitely has a sedative effect. Eastman explains: "It's the way the internal circadian clock tells the body what time it is. Melatonin is the 'dark signal.'" Through careful adjustment of light exposure (the main signal that the SCN uses to "set" the body's internal clock by controlling the flow of melatonin from the pineal gland) and sometimes administering extra melatonin with pills, Eastman has demonstrated that it's possible to phase-shift night workers' circadian clock to a new rhythm—which can help them get the sleep they so critically need.
Strategies include exposing shift workers to controlled amounts of bright light with the use of light boxes at work, then limiting their light exposure after their shift by having them wear sunglasses on their commute home (to reduce the amount of light reaching the SCN through the eyes), as well as going to sleep immediately after getting home in as dark a room as possible.
Still, maintaining such lifestyle changes can be difficult. "Sometimes society is working against you, wanting you to do things in the morning," Eastman says. "For night shift workers to do it right, they have to have cooperation from their employer in the form of bright light at work. They need cooperation from their family to let them sleep late on days off and after the night shift. The world has to be sympathetic to the fact that it's really hard to do shift work."
Often, the most difficult step toward improving your sleep is realizing that not sleeping enough is indeed a real problem. With some relatively simple shifts in habit, we can all help ourselves to get better rest.
For example, while you may have stopped keeping a regular bedtime decades ago when your mother stopped tucking you in, sticking to a sleep schedule—one in tune with your natural proclivity towards being a night owl or an early bird—in which you hit the sack at the same time each night, is important.
If you find that your schedule is at odds with your natural sleep preferences (say you must leave for work by 6 a.m. but don't become sleepy until midnight) you can help prime your body to drift off on the earlier side by manipulating the sleep homeostat. Our bodies naturally experience a sharp drop in temperature at the onset of sleep, and you can recreate this process by taking a hot bath or shower just before you get into bed. As your body cools off afterward, it will help usher in a feeling of sleepiness.
Simply unplugging is also wise. The thought of leaving your laptop at the office or not checking your iPhone before bed might make you anxious, but limiting technology use after dark—particularly in the bedroom—is critical. "Just getting light from computer and other screens before bed can throw off your circadian cycles," notes fatigue researcher Mark. R. Rosekind. "Data show, for example, that kids with technology in their bedroom—video games, tablets, phones—get up to two hours less sleep than those without it."
You might even consider installing dimmers on your light switches and then lowering the lights in the hours leading up to bedtime. "Light exposure in the evening makes us more alert, pushes our rhythms later, and suppresses the normal secretion of melatonin," Harvard biologist Jeanne Duffy explains. "Even if you're just in regular room light in the evening, nothing bright, it will have a biological effect—probably resulting in your going to bed later, which can shorten sleep overall," she says.
Taken together, such small changes can engender a significant—and lasting—improvement in the quality of your nights. "It's not as if you have to have surgery or take a pill,"observes the University of Pittsburgh's Martica Hall. "Sleep is a modifiable challenge."