As the world awakens more and more to systemic racism and racial disparities in healthcare, we examine sleep — a key component of health. Are there racial disparities in the amount of shut-eye that Americans get? Do Black adults in the United States get less sleep than white adults, and if so, why? These are some of the questions that we investigate in this feature.
Sleep is a vital component of health. Its benefits range from better concentration, sharper cognitive skills, and a stronger immune system to lower risks of excess weight gain, cardiovascular disease, and depression.
The Centers for Disease Control and Prevention (CDC) recommend that people aged 18–60 get at least 7 hours of sleep every night. But not everyone can afford to sleep as much as they should. According to 2016 estimates, as many as 1 in 3 adults in the U.S. were not getting enough sleep.
But how does the racial breakdown look? Are people of color just as sleep-deprived as white people?
In the context of COVID-19 and the impact that preexisting conditions such as heart disease and diabetes have on the severity of the illness, it is all the more important to ask — does poor sleep contribute to a higher risk of these conditions among African Americans?
An established body of research highlights racial disparities in sleep. For example, in 2015, a team led by Prof. Girardin Jean-Louis — from the Center for Healthful Behavior Change at New York University’s Grossman School of Medicine — used data from the National Health Interview Survey to examine sleep trends among tens of thousands of white and Black Americans between 1977 and 2009.
The researchers found that during this period, Black respondents were consistently more likely to have very short sleep or short sleep, compared with their white counterparts.
The team defined very short sleep as less than 5 hours a night and short sleep as between 5 and 6 hours.
The study found that by 2009, 2.3% of white respondents routinely slept less than 5 hours and 25.4% slept between 5 and 6 hours per night. In comparison, 4.0% of Black respondents reported very short sleep, and 33.7% reported short sleep.
These findings, note the researchers, were consistent with those of previous studies indicating that Black adults were almost twice as likely to sleep less than 7 hours per night, compared with white adults.
Racial differences exist not just in the amount of sleep, but also in the quality, or “architecture,” of sleep. Some studies have found that African Americans tend to not spend as much time in deep, slow-wave sleep as white Americans and are thus more likely to report physical fatigue.
The relationship was mediated by perceived discrimination, meaning that:
“Individuals who reported experiencing more discrimination had less stage 4 [deep] sleep and reported experiencing greater physical fatigue.”
– Kamala S. Thomas et al.
Prof. Jean-Louis and colleagues write, “Black very short-sleepers may be at greater risk of experiencing deleterious physiologic and hormonal effects of insufficient sleep, which may predispose them to adverse cardiometabolic outcomes.”
Indeed, numerous studies and sleep curtailment experiments have shown a strong connection between poor sleep, obesity, and cardiovascular conditions.
Research indicates that poor sleep disturbs many metabolic pathways, “leading to more insulin resistance, possibly decreased energy expenditure, increased appetite, and immunological changes.”
More specifically, zooming in on immunological pathways, several studies have found increased plasma levels of a pro‐inflammatory cytokine called interleukin 6 after partial and total sleep loss.
In turn, pro-inflammatory cytokines such as interleukin 6 have been associated with a higher risk of cardiovascular disease and diabetes.
So, the sleep deprivation that seems to be more prevalent among Black adults may well account for some chronic conditions — such as high blood pressure, overweight, obesity, and diabetes — to which this group is more predisposed.
There are several possible reasons for these disparities.
As Prof. Jean-Louis and the team note, untreated sleep apnea may be partly to blame. The condition is far more prevalent among Black Americans, with one study, for instance, finding that 31% of Black participants had sleep apnea, compared with 10% of white participants.
Some have wondered whether genes and circadian rhythms play a role in sleep disparities. However, research has found that when people sleep in controlled environments, such as sleep labs, most of the disparities disappear.
For instance, a meta-analysis of 14 studies that included more than 4,100 total participants looked at sleep efficiency, total sleep time, and sleep latency in African Americans, compared with European Americans. The analysis found that the disparities “were only present in community-based studies, but not in studies where participants were examined in a laboratory setting, where time in bed is controlled.”
This suggests that cultural and social factors may be to blame. Prof Jean-Louis and colleagues list some of these factors that may explain sleep disparities among people of color:
- Urban residence: A study of almost 33,000 adult participants found that among Black and Hispanic adults, inner-city living was associated with an “increased risk of short sleeping and reduced risk of long sleeping,” compared with living in nonurban areas.
- Work schedule: A Population Reference Bureau report shows that Black and Latinx Americans are disproportionately more likely to work unconventional hours, compared with white peers — while shift work is known to disrupt sleep.
- Job strain: Black immigrant workers are almost three times more likely to experience job-related stress than white workers, some studies have found, a disparity likely explained by discrimination in the workplace.
Furthermore, a “lack of emotional support, perceived discrimination, types of industry and occupation, and high burden of chronic medical conditions” may also explain sleep disparities, Prof. Jean-Louis and colleagues explain.
While the reasons behind these gaps in sleep may be somewhat unclear for now, one thing is certain: Race-related sleep disparities disproportionately affect the Black population in the U.S.
Sleep deprivation contributes to further disparities in chronic conditions, by causing more of these illnesses in Black people or by exacerbating them.
“When viewed in the context of health equity research, insufficient sleep may be a key factor in understanding diseases that disproportionately burden [Black adults]. Whether sleep time in this population is curtailed by lifestyle choices or restricted by sleep fragmentation, as is the case in sleep apnea, [Black Americans] may be at increased risk of developing chronic diseases (e.g., diabetes and cardiovascular disease) due to insufficient sleep.”
– Girardin Jean-Louis et al.