Last spring, campus police officers at Yale University responded to a call from a white graduate student about a black graduate student, whom she said was unknown to her and sleeping in the common room. For many, the incident was further evidence that African Americans are targets of harassment even in ostensibly “safe” spaces, but the interaction is also a window into another, less-publicized disparity: It’s likely that, over the course of their lifetimes, the white student has slept hundreds of hours more than the black student.

According to a forthcoming paper by Tiffany Yip, a psychology professor at Fordham University, the sleep gap between white and nonwhite students begins with children as young as 2 years old — and it grows from there. What starts as a 15 minutes-a-day sleep deficit in childhood eventually becomes almost an hour a night in adulthood.

But it isn’t just a difference of time. According to a study conducted by the National Sleep Foundation, African Americans are more likely than Caucasians to have insomnia, sleep apnea and daytime sleepiness. In addition, they spend 15 percent of their night in deep sleep (considered the most restorative phase), compared with Caucasians’ 20 percent.

Lauren Hale, an assistant professor of preventive medicine at Stony Brook University, calls the sleep gap “a matter of social justice” and identifies two other significant predictors in addition to race: Level of education (those without a high school diploma are more likely to have sleep disorders) and neighborhood context (city dwellers typically sleep less than those outside the urban core). Hale says of her findings, “If the very people who are the most socially disadvantaged and most need that extra boost to function better during their days wake up the least prepared, then they are at a disadvantage throughout every aspect of their day.”

Of course, race also is intertwined with education levels, ZIP code and other factors that impede a restful night’s sleep, such as crowding and cigarette smoking in the home and living in a higher-crime neighborhood. But Yip says, “there are still independent effects of race that go above and beyond socioeconomic effects.”

Studying teens

To study the sleep gap among adolescents, Yip recruited 146 participants from five public high schools in New York City. For two weeks a year, the freshmen self-reported their sleep length and quality, in addition to wearing a device similar to a sophisticated Fitbit, which tracked their activity 24 hours a day.

Using teenagers was especially helpful for Yip’s research because adolescence is typically when our brains develop enough to be able to form a racial identity. Yip says, “Seeing discrimination in the world as it happens to people of different racial, ethnic groups, as it happens to people in your own racial, ethnic groups, as it starts to happen to friends and family members and as well as yourself — all of those things require a pretty sophisticated cognitive understanding.”

As teenagers start to process these events, they become more sensitive to discrimination, whether it’s a major traumatic event, such as not getting fair housing, or whether it’s a more mundane event, sometimes called a microaggression, such as an African American being complimented for being “very articulate.”

Both kinds of discrimination negatively impact sleep, which starts a negative feedback loop. Chronic sleepiness can make it more difficult for teenagers to regulate their emotions, which sharpens the blow of discrimination, further disturbing their rest. In that regard, Yip thinks of sleep as a “biological mechanism” that links stressors, such as discrimination, with more tangible outcomes, such as weaker academic performance or more frequent symptoms of depression and anxiety.

Bridging the gap

Fully closing the sleep gap would require addressing all of the societal factors that have created it, such as structural racism, but Yip points out that even being aware of the relationship between discrimination and sleep disturbance is positive. This is especially true after someone has experienced an event that isn’t overtly racist, as they think of “all the things they could’ve done differently.” Yip says, “If we can do some of that processing before bedtime, I think that might help to alleviate some of the disparity.”

Of the many disparities in health between white and nonwhites, the sleep gap has received relatively little attention. For example, it’s unknown whether the gap is affected by the level of racial integration in a neighborhood. Yip also was surprised to discover that it was actually Asian-American teenagers who slept the least of any racial group — 45 minutes less than their Caucasian peers. That difference, she believes, might be explained by the source of the discrimination against them.

“African-American children experience discrimination from teachers and police officers and adults,” she says. “The Asian kids experience more discrimination from peers.” She hopes to test that thesis on an upcoming study of college students.

Across the board, though, Yip has one recommendation: Don’t disregard the importance of sleep. “I think if we can underscore that a little bit more, then I think that people will appreciate the importance of going to bed rather than staying up all night to study for an exam.”