In 2005, researchers at the University of California, San Diego, began an experiment that would last five years. One by one, they brought 164 study participants to a sleep lab at the U.C. San Diego Medical Center, a room with a sweeping view of the city and the surrounding valley. There, participants underwent polysomnography, the most comprehensive sleep test known to science. A polysomnography machine is an octopus of a medical device: It has scalp sensors to record brain-wave patterns; eye trackers to assess rapid eye movements; breathing sensors that are placed on the nose, mouth, and around the chest; a blood-oxygen sensor for the fingers; and sensors on the legs to track movement. The machine produces a chart—resembling a cross between a musical composition and a seismogram—that traces the brain and body minute by minute through the night.

The San Diego researchers planned to use the polysomnography machine to document slow-wave sleep—the phase of sleep “when it’s really hard to wake you up,” as Tomfohr describes it. Slow-wave sleep is thought to be the most restorative period of sleep, and it’s important to good health: Experiments where people are denied slow-wave sleep on purpose have shown that bodies quickly change for the worse. (One paper, published in the Proceedings of the National Academy of Sciences in 2007, found that study participants who were denied slow-wave sleep for three nights—researchers would sound an alarm in their ears when they entered this sleep phase—became less sensitive to insulin, a precursor to diabetes.)

But it wasn’t just slow-wave sleep in general that interested the researchers; they specifically hoped to compare how blacks and whites experienced slow-wave sleep. And what they found was disturbing. Generally, people are thought to spend 20 percent of their night in slow-wave sleep, and the study’s white participants hit this mark. Black participants, however, spent only about 15 percent of the night in slow-wave sleep.

The study was just one data point in a mounting pile of evidence that black Americans aren’t sleeping as well as whites. This past June, the journal Sleep published a study on the sleep quality of black, white, Chinese, and Hispanic adults in six cities across the United States. The participants were pooled from the Multi-Ethnic Study of Atherosclerosis (MESA), a cohort of more than 6,000 people who, for the last 15 years, have been intermittently pricked, prodded, and assessed to discover how geography and race influence health over time. (More than 950 papers have been published on this cohort. It’s from them that researchers have found evidence that the farther people live from a wealthier area, the more likely they are to develop insulin resistance—or that blacks appear to have higher levels of the substances that cause blood to clot.)

For a week, participants in the MESA study wore actigraphy bands, Fitbit-like bracelets that can estimate the amount of time a person is asleep. In a separate test, they underwent polysomnography. The results? “The insufficient amount of sleep, the short sleep duration of the African Americans really stood out,” says Susan Redline, a Harvard professor of sleep medicine and one of the study’s co-authors. “It really emphasized that African Americans, as a group, are getting the least amount of sleep compared, at least, to the three other groups.” Whites in the study slept an average of 6.85 hours; blacks slept an average of 6.05 hours.

Compared with white participants in the study, black participants—most epidemiologists prefer “black” to African American; it encompasses more people—were five times more likely to get short sleep, defined as less than six hours a night. (Hispanic participants were 1.8 times more likely to get short sleep; Chinese participants were 2.3 times more likely.) Blacks were also more likely to report feeling sleepy in the daytime, and they woke up more often in the middle of the night. “Notably,” the study reads, “these associations remained evident after adjustment for sex, age, study site, and [body mass index].”

Fifteen years ago, the intersection of sleep and race wasn’t studied much at all. Researchers in the sleep field “hadn’t really thought about this idea—by race, by economic status—that people had different amounts of sleep,” says Diane Lauderdale, an epidemiologist at the University of Chicago. In the early 2000s, Lauderdale was part of an effort that was one of the first to find racial differences in sleep using objective measurements, as opposed to self-reports. Studying a 669-person cohort in Chicago—44 percent were black; the rest were white—she and her colleagues found, on average, an hour difference between blacks’ and whites’ sleep.

What’s more, the sleep discrepancy persisted even when the researchers tried to control for economic factors: As blacks got wealthier, the gap in sleep narrowed, but did not go away entirely. “The race gap is decreased if you take into account some indicator of economics,” says Lauderdale, “but it’s not eliminated in the data that I have looked at.” Indeed, in the San Diego study, researchers also concluded that there were racial differences in sleep regardless of income. (It should be noted, however, that researchers concede their attempts to control for economic indicators are far from perfect. “We know our measures for adjusting for socioeconomic status are still somewhat limited,” says Redline. “Sometimes the variation isn’t great enough.”)

So what explains the gap? It’s an intriguing and still somewhat open-ended scientific mystery. (And one that is that gradually getting more and more attention: In July, the radio program Freakonomics dedicated a segment to documenting the discrepancy and trying to explain why it might exist.) But the black-white sleep gap isn’t just a question for science; it also has implications for the policy world. Sleep, after all, may be a key factor in a tragic spiral: It appears to be both a symptom of health problems that disproportionately affect black communities and also a cause of those same problems. Which is why it seems worth asking: Are there policy interventions that could, realistically, help to improve how black Americans sleep?

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For most of human history, the question “why do we sleep” has been an absolute unknown. Before William C. Dement conducted the first overnight sleep recordings of brain activity in the early 1950s, our knowledge of sleep was “prehistoric,” he wrote in a 1998 essay, “The Study of Human Sleep: A Historical Perspective.” Prior to that point, the prevailing theory was that sleep was simply when the brain went dormant, recovering its energy to begin a new day. Sigmund Freud himself dismissed sleep’s significance. “I have had little occasion to concern myself with the problem of sleep, as this is essentially a physiological problem,” he wrote. To him, sleep was subservient to dreams, which were the mind’s way of channeling away anxieties and perversions.

In 1953, the discovery of REM (rapid eye movement) sleep set off a rush of research into what was happening inside the brain at night. Scientists found the sleeping mind wasn’t dormant at all, but engaged in a flurry of structured activity. We progress through the night in a choreographed order: from light sleep, to deep sleep, to REM, and then back again. We dream in REM—the most active phase of sleep—but the brain is busy throughout the night. In the quieter stages, the brain is still 80 percent activated, “and thus capable of robust and elaborate information-processing,” a 2005 article in the journal Nature explains. Sleep is when the brain reorganizes itself and consolidates memories; it’s essential for learning and concentration. (Multiple studies have, for instance, found that after daylight savings time begins in the spring—a day when people are likely to have their sleep disrupted—the number of traffic fatalities increases.)

While sleep is crucial for day-to-day functioning, it’s also crucial for health. As psychologists were discovering the architecture of sleep, epidemiologists were beginning to assess its impact on our bodies. “In the 1960s, there were a number of large community-based studies that sought to figure out what the real causes of death were in the community,” says Michael Grandner, the director of sleep and health research at the University of Arizona. Large-scale epidemiological projects like the Framingham heart study (begun in 1948) and the Alameda County study (begun in 1965) helped to create the maxims that dominate public health to this day—smoking kills, diet and exercise factor into heart disease, alcohol is dangerous—but hidden in all that data was another finding: In meta-analyses of these large-scale studies, “you get this u-shape for mortality,” Grandner says. Both too much sleep (longer than eight hours) and too little sleep (shorter than six hours) put people at higher odds for early death. (According to Grandner, there’s a clearer consensus around the idea that too little sleep is bad for health; the effects of too much sleep remain an open and debated question.)

In 2002, Grandner’s mentor, Daniel Kripke, a psychiatrist at the University of California, San Diego, published a report compiling data from more than 1 million men and women aged 30 to 102. “The best survival was found among those who slept seven hours per night,” the study found. Says Grandner: “This was, and still is, the largest study ever on this topic and arguably the most clear.”

To understand why scientists hypothesize that poor sleep causes poor health, we need to dive into the smallest components of the human body. It is here scientists have made the biggest leaps in connecting sleep with overall health. Over the last two decades, there has been a shift in the way scientists understand sleep, explains Allan Pack, who researches sleep and genomics at the University of Pennsylvania’s Perelman School of Medicine. “The idea was you go to sleep, the brain shuts down, something happens that’s helpful to” your brain, Pack says. Now, however, “one of the things we know is there’s not only a clock in your brain controlling the sleep-wake pattern, there are clocks in every tissue, essentially.”

Scientists have discovered “clock genes,” tiny bits of DNA that act like a biological metronome: By regularly flipping on and off, they help the body maintain its sense of time. And not only are these clocks in every tissue in every human, or in every tissue in every mammal, but they can be found in “virtually every organism on the surface of the planet,” says Michael Twery, the director of the National Institutes of Health’s National Center on Sleep Disorders Research. Cycles in activity and rest are fundamental in the architecture of life.

Messing with these cycles—essentially throwing the body’s metronome off beat—throws the whole body off beat. “When you have situations like the mistiming of sleep, or not enough sleep, you can conceivably alter clock [gene] function and then alter the expression of all these important genes that are regulating things like metabolism, or skeletal muscle function, pancreatic function,” says John Hogenesch, a chronobiologist at the University of Pennsylvania who studies clock genes in mammals. Like toxins in the food chain, the effects accumulate upward from there: Cells that have their clock genes disrupted don’t produce the right proteins, those proteins then don’t regulate tissues well, and organ systems show strain.

In the late 1990s, an invention called the microarray—a computer chip that allows researchers to study how many genes are turned on in a given cell—burst open this research. Now, scientists could watch, in near-real time, what was happening to cells in animals that had been denied sleep. They didn’t look healthy. “When you keep animals awake, you get this phenomenon called the unfolded protein response,” Pack explains. Proteins are the building blocks of the cell. If the proteins are poorly constructed, or, in science speak, unfolded—like a Lego block with a misshapen connector—they won’t work. “Then you either have got to destroy them or what happens is they aggregate into lumps,” Pack says. “And you get these protein aggregates, which are very toxic to the cell.”

How those disruptions in the cell come to affect entire organ systems isn’t entirely understood. But evidence from molecular biology, epidemiology, and psychology points to the idea that poor sleep is a risk factor for heart disease, diabetes, and obesity—which are all ailments that disproportionately affect black communities. In America, blacks are 33 percent more likely to die from heart disease than the population at large, 1.7 times more likely to have diabetes, and 1.5 times more likely to be obese. For every 100,000 blacks, it’s estimated that heart disease takes away 1,691.1 years of potential life in a given year. For whites, that figure is 900.9 years.

Overall, if we factor out deaths caused by aging, the mortality rate for black men—from all causes—in the United States is 1,104 per 100,000, according to the Centers for Disease Control and Prevention. For white men, the mortality rate is 878.5 deaths per 100,000. For white women, that figure is 630.8 per 100,000; for black women, it’s 752.5. Could sleep explain part of the difference between blacks and whites?

The best scientists are always skeptical, and the sleep researchers I spoke to were no exception. “It’s plausible to suggest racial differences in sleep, whatever the cause, might potentially be one, maybe a small piece,” Grandner says. “It’s probably not explaining the whole thing or a large fraction of it, but could be playing a role in some of these health disparities.”

One thing, however, is certain: Sleep disparities do exist. “I think we can say there’s a great deal of evidence that there are race differences,” Lauderdale says. And given the link between sleep and well-being, it seems clear that those differences are worth taking seriously as a matter of public health.

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On the question of how to explain the black-white sleep gap itself, researchers have a number of related theories. (There is a consensus that innate biological differences between blacks and whites are not a factor.) The stress caused by discrimination is one strong possibility. In the San Diego sleep study, Tomfohr’s team knew, going in, that slow-wave sleep is very sensitive to stress—which is, in turn, our body’s signal to remain vigilant against perceived threats, including discrimination. “That was our thought: If people are feeling really discriminated against, then of course they are not going to want to get into a really deep stage of sleep,” she says.

After the participants’ stays in the San Diego lab, researchers had them take a survey, designed to assess the level of discrimination they felt on any given day. (Participants were asked to agree or disagree with statements, including “In my life, I have experienced prejudice because of my ethnicity” and “My ethnic group is often criticized in this country.”) Armed with this information, Tomfohr and her colleagues could then determine a correlation between discrimination and sleep. And it turned out that there was, in fact, a correlation: More discrimination meant less slow-wave sleep. “If you can take out that discrimination piece, the average African American and the average Caucasian look at lot more similar,” she says. “It’s not perfect, but in terms of sleep, a lot of the disparity goes away.”

Danielle L. Beatty Moody, a psychologist at the University of Maryland, Baltimore County, conducted a similar test while working as a post-doctoral scholar in the psychiatry department of the University of Pittsburgh in the late 2000s. People who are discriminated against, she believes, carry worry throughout the day. And that worry literally keeps them up at night. “It’s uncomfortable for them to sleep because they are thinking back over mistreatment, thinking back over maltreatment, thinking back over bias they experienced,” she says. “In thinking about those experiences, they are getting more aroused, more cognitive arousal, which does the opposite of what you need it to do to go to sleep.”

Lauren Hale, a professor of preventive medicine at Stony Brook University and the founding editor in chief of the journal Sleep Health, makes a similar but slightly different point: She argues that sleep is a reflection of a person’s agency. The more control you have over your life—the more freedom you have financially, the more freedom you have to live where you choose, the more control you have over what you eat and when you eat it, the more you have the luxury of possessing the time and equipment to exercise—the more likely you are able to create an environment that fosters good sleep. “[S]keptics cannot argue that people with poor sleep habits simply ‘choose’ to sleep poorly,” Hale and a co-author wrote in 2010. “Sleep should be viewed as a consequence of something other than choice.”

Neighborhoods also appear to matter when it comes to sleep health. “I have never seen a study that hasn’t shown a direct association between neighborhood quality and sleep quality,” Hale tells me. “Those two are linked.” And black families are more likely to live in poorer neighborhoods, even if they are middle-income. (“Even among white and black families with similar incomes, white families are much more likely to live in good neighborhoods—with high-quality schools, day-care options, parks, playgrounds and transportation options,” wrote David Leonhardt recently in The New York Times, summarizing the results of a Stanford study by Sean Reardon.)

Feelings of safety are key here. Hale theorizes that—as with discrimination—noisy, unsafe, disorderly neighborhoods increase stress and the need for vigilance. “If you know somebody in your neighborhood who has had a break-in, you might feel pretty uncomfortable shutting your eyes falling asleep while your two or three children are sleeping in the room next door and no one else is there to protect them,” she says. “And that type of insecurity, whether it’s financial or physical safety, is more common among people who don’t have control over their environment, because if you did have control over your environment, you’d say, ‘I’m getting out of here.’”

Hale has been involved in several studies that compare levels of disorder in a neighborhood—as measured by cleanliness, crime, presence of graffiti, and so on—with sleep and health. Overall, she finds, poor sleep can explain 20 percent of the difference between the good health found in rich neighborhoods and the bad health found in poor ones. “Based on these results, targeted interventions designed to promote sleep quality in disadvantaged neighborhoods (e.g., community-based sleep promotion and noise-level ordinances) could help to improve the physical health of residents in the short-term,” Hale writes in one of her co-authored papers in the journal Preventive Medicine. And while “community-based sleep promotion” may sound like an impossibly vague intervention, there are, in fact, programs underway that show how it might be done.

* * *

Some of the more practical research aimed at helping black Americans to sleep better is being conducted by Girardin Jean-Louis, a charismatic Haitian-born psychologist who runs a lab dedicated to sleep and health disparities at New York University’s Center for Healthful Behavior Change. When I first started reporting on this topic, Jean-Louis’s name was brought up in just about every conversation. “What I think is innovative about what Dr. Jean-Louis is doing is that he goes into the community and finds out from the stakeholders what we need to do and works with them,” says Kristen Knutson, a biomedical anthropologist at the University of Chicago who has been studying the link between sleep and health outcomes.

It’s 84 degrees and rising on a Saturday in August when I go to see Jean-Louis’s work in action. In the St. Albans community of Jamaica, Queens, Azizi Seixas—a member of Jean-Louis’s team—takes the stage outside Christ Church International. Congregants and community members sit under tents in the closed-off street adjacent to the church, which, despite its coral-pink bricks, is as nondescript and industrial as the self-storage facility next door.

Today is the church’s annual health fair. Six tents line the street. At one, passersby can get their blood pressure or blood-sugar levels taken (though I don’t see any who do). Another station is giving away free reflexology foot massages (much more popular).

Seixas is here to recruit participants for a yearlong study that Jean-Louis’s lab is conducting. St. Albans—a working- to middle-class community that is almost entirely black—isn’t the poorest neighborhood in the city, but it suffers from the same stressors as many other minority areas: people working multiple jobs at odd hours; people struggling to pay for mortgages while taking care of their families. “People have two or three jobs—they don’t get enough sleep,” the nurse manning the blood-pressure station tells me. “You come in [from one job], you get five or six minutes sleep—or maybe two hours of sleep—then you have to go out to another job. They don’t realize. They just think, ‘Oh, I’m tired.’ They don’t realize they’re developing a problem that’s greater than being just tired.”

Thirty percent of adult residents in the greater Jamaica area are obese. The death rate from diabetes in Jamaica is higher than in both Queens and New York City as a whole. Jamaica also has one of the highest rates of heart-attack hospitalizations in the city. “When you don’t sleep well, guess what happens?” Seixas asks the crowd from the stage. “Over time, that builds up, and it builds up, and it builds up, and what we have found is that many of the times, the hypertension—the high blood pressure—the diabetes, all those health conditions are associated. They have something to do with sleep.”

Seixas directs those assembled to a station that NYU has set up for free sleep screenings. They’ll ask for history of snoring, insomnia, and daytime sleepiness. Their specific target is to identify people at risk for obstructive sleep apnea, a potentially deadly disorder where a person intermittently stops breathing during sleep. These cessations, called apneas, can occur hundreds of times in a night, and each generally lasts 10 to 30 seconds.

People with sleep apnea get truly awful sleep. Essentially, it’s a condition that maximizes all of the health problems related to short sleep duration. Like short sleepers, people with sleep apnea are at higher risk for high blood pressure, diabetes, and weight gain. “We take some of these people with hypertension, and we give them antihypertensive medications. Often times, what we find is there is a subset of people, primarily blacks, where they don’t respond to the hypertensive medication,” Seixas tells me. “What we found in our studies is that a lot of these people have undetected, untreated sleep disorders, particularly sleep apnea.”

As with sleep problems more generally, there is a racial disparity when it comes to sleep apnea. “Not only does it seem like they’re more likely to have the disorder, they’re less likely to make it to a doctor to have treatment prescribed, and even if they get treatment prescribed, they’re less adherent and don’t use it as much,” Knutson says. “So, all across, from step A to step Z of getting treated, there are disparities.” In the June Sleep report, 12.8 percent of blacks in the cohort had sleep apnea; 7.4 percent of whites did. An overview paper in the 2015 Annual Review of Public Health cites 14 percent of blacks as having the condition—the figures for whites are around half that—and also states that sleep apnea is four to six times as prevalent in black children. (It’s hard to say how prevalent sleep apnea is—among blacks, whites, or in the overall population—because apneas are usually so short that people don’t remember waking up from them.)

Apnea is just one aspect of Jean-Louis’s work on sleep. One unit of his lab is looking into the noise levels of different New York neighborhoods and then determining their impacts on sleep and blood pressure. In another program, the lab is restricting one hour of sleep in a group of adults for 12 weeks to see how the change affects their bodies. They also have an NIH-funded program designing a website for sleep-health education. When I visit their offices a few days after the health fair, the team—a diverse collection of academics in their 20s and 30s—is debating whether a stock image of a black man sleeping next to a bowl of food is appropriate for the education website.

Until 2000, Jean-Louis was focused on lab-based work at the University of California, San Diego, researching under Daniel Kripke. But he found that the controlled, sterile environment wasn’t satisfying. “You have got to be in the community where you are actually touching people’s lives,” he says. “To me, this is more rewarding.”

While Jean-Louis was in San Diego, evidence was mounting that not only were blacks not getting good sleep but they were more at risk for sleep disorders. San Diego is only about 5 percent black—a figure not conducive to research on race—so Jean-Louis took a position at SUNY Downstate College of Medicine in Brooklyn, a place where he just had to step outside to be immersed in the black community. He and his childhood friend and frequent collaborator Ferdinand Zizi—a sleep-health researcher as well—would go to churches, barber shops, beauty salons, and community centers to recruit people for focus groups and find out what was holding their sleep health back.

What they found was a community unfamiliar with sleep health and hesitant to undergo lab tests. One of their studies tracked 421 black patients who were referred to get tested for sleep apnea. Just 38 percent showed up to get a diagnosis (even though all were called by the doctor to remind them of their appointments). Of those 38 percent, nearly all received a positive diagnosis. Many of those referred for sleep tests were obese, hypertensive, and had high cholesterol. Missing out on sleep treatments meant they were missing out on an opportunity to manage those conditions as well.

Jean-Louis joined NYU in 2013. In his current study—which is being funded by the NIH at a cost of $423,750—he and his colleagues are trying to figure out whether simple interventions could better diagnose and treat minorities for sleep apnea. (For the first year, the study was only for blacks; now it has been opened up to all minorities.) Hence the team’s visit to places like Christ Church International. “Girardin’s studies are pioneering,” says Twery of the NIH, “in the sense he is doing community-based research to understand the cultural basis of the problem and how to improve the health of these communities.”

At the health fair, if community members are identified as being at risk for sleep apnea, they’re invited to join the study. Once in the study, they are first assigned a peer health educator. This person, who usually lives in the same community, guides the participants through the process of getting a diagnosis and then helps them adhere to treatments.

“People like stories. They like you to engage them,” Jean-Louis says. “So you might find the first five to ten minutes, you’re just talking about their lives.” He believes this is the key aspect of the intervention. The idea is to be sensitive to any wariness patients may have of medical institutions and not to blame them for lacking knowledge. In his papers, he calls this approach culturally tailored education. “When people feel you value them, you value their time, they’ll do it. But you just can’t show up with a clipboard and asking questions,” he explains.

The health educators—who have six weeks of training—remain in contact with the participants for a year, acting as health coaches and guiding them toward treatment goals. “Until people are able to understand what sleep apnea is about, they’re going to be resistant,” Lystra Harry, one of the educators, tells me. “Whatever decision they choose to make, we respect it.” Not everyone will get a diagnosis, but everyone will be educated in sleep health, which could help alleviate problems of short sleep as well.

Jean-Louis says he has preliminary data that shows this approach is working. People who receive culturally tailored sleep education are, he says, four times more likely to make an appointment for a follow-up exam. “And once they are in, they will actually stay in,” he says.

For privacy reasons, the NYU team wouldn’t put me in touch with any participants in the study. But the lead peer health educator introduced me to her sister, Kimberly Turner, a 55-year-old African American resident of Canarsie, Brooklyn, who had been diagnosed with sleep apnea. Before she was diagnosed, she told me, she felt like she was in the Twilight Zone. Time seemed to disappear. A coworker sitting next to her would suddenly vanish. She’d stop at a red light and then, an instant later, car horns would be blaring at her. She would wonder: “Did that really happen?” She hadn’t realized she was falling asleep during the day. “You start to question everything,” she says.

Turner was tired all the time. She woke up with terrible headaches. All the clues pointing toward apnea were there, but she didn’t realize something might be wrong with her breathing during sleep until her husband told her. “He just literally said that I stopped breathing, and I was like, ‘You’re kidding me, I don’t stop breathing.’ I had never really heard of it at that point.”

On the advice of her doctor, she was referred for an overnight polysomnography sleep study. It took some convincing (“You have to sleep in this unknown place the whole night, and I didn’t want to do it”), but she eventually agreed. Two minutes into Turner’s sleep study it had to be stopped. “I stopped breathing too many times,” she says.

After being diagnosed, Turner was prescribed a CPAP (continuous positive airway pressure) mask to wear at night. It’s cumbersome and “a mood killer,” she says, but it keeps her airways open. Since treatment, her life has turned around. She’s more alert. Her headaches are gone.

The theory guiding Jean-Louis’s work is that sleep disorders like Turner’s are a significant contributor to racial health gaps in this country—and if we could treat all those cases, there would be a meaningful reduction in health disparities. “Untreated sleep apnea leads to cardiovascular disease if not death,” Jean-Louis says. “There are many times we go, we give talks in churches, and we hear stories of people who died, and we always say to ourselves, ‘You know, I think that was untreated sleep apnea.’ We can’t have a 35-year-old African American male go to bed and not wake up the next day. That doesn’t make any sense.”

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Sleep apnea is the most extreme manifestation of the sleeping problems that disproportionately affect black Americans. But focusing on community-based health education—as Jean-Louis is doing—may help not just with sleep apnea but with other sleeping problems, too. And if his interventions work, they could be scaled up.

Indeed, whether it’s through community health fairs or schools, sleep education probably needs to become more widespread. “What really brings me hope is that in a conversation with new parents or a conversation with middle-school students and their teachers, you can have a tremendous impact,” says Orfeu Buxton, a sleep-medicine researcher with appointments at Harvard and Penn State who occasionally gives talks at schools. The benefits of good sleep aren’t hard to market. “You talk about being happy, looking better, being healthier, all these different things, and I don’t know which one is going to hit for which person, but once you give the explanation of how big an impact sleep has on absolutely everything, younger people are turning the corner, I think.”

For kids, Buxton thinks that having schools start later would encourage healthy sleep habits at an early age. For adults, workplaces can also adjust: Buxton and colleagues at Harvard have found that in nursing homes where managers were more supportive of work-life balance, employees were more likely to get more sleep.

Both state governments and Washington could play a role by encouraging employers to adopt company wellness programs that reward good sleep. (Most critically, these programs should seek to reach shift workers who live in an almost constant state of jet lag.) In fact, at every level of government, there are policy decisions—whether on neighborhood noise levels or public safety or the placement of public housing—that provide good opportunities to consider, and perhaps improve, how people sleep.

One point of optimism is that this subject, though relatively new, is being well-supported by the NIH. The majority of the studies cited in this article received some funding from the NIH, which has identified decreasing health disparities as a research priority. Since 1993, according to Twery, there have been more than 10,000 NIH-funded sleep research projects published.

Ultimately, sleep may offer researchers a way to attack seemingly even more intractable health problems—including those that disproportionately affect black Americans. “Not only might sleep be a potential causal factor in health disparities making things worse, it might be a potential place to help the situation,” Grandner says. “If you take someone who is not getting enough sleep, and you increase their sleep, can that prevent some of these things”—obesity, diabetes, heart disease—“over time? That’s still an open question.”

Tomfohr also sees some cause for optimism. “I don’t think this is totally fatalistic,” she says. “My hope is that this is addressable from multiple levels—that we can identify people who are at risk for sleeping poorly, and then we can do good interventions to help them sleep better, so this isn’t a sentence towards getting cardiovascular disease, or getting sick, or getting diabetes. I have a hopeful feeling about this.”