As the world wakes up more and more to systemic racism and racial disparities in healthcare, we’re looking at sleep — a key component of health. Are there racial differences in the amount of eyes that Americans get? Do black adults sleep less than white adults in the United States, and if so, why? These are some of the questions we explore in this feature.
Sleep is an important part of health. Its benefits range from better concentration, sharper cognitive abilities, and a stronger immune system to lower risks of weight gain, cardiovascular disease, and depression.
The Centers for Disease Control and Prevention (CDC) recommends that people aged 18 to 60 get at least 7 hours of sleep each night. But not everyone can afford to sleep as much as they should. According to estimates from 2016, up to 1 in 3 adults in the USA did not get enough sleep.
But what does the racial collapse look like? Are people of color as sleepless as white people?
In connection with COVID-19 and the impact of pre-existing conditions such as heart disease and diabetes on the severity of the disease, it is even more important to ask: Does poor sleep contribute to a higher risk of these conditions among African Americans?
Health inequalities affect us all differently. Visit our dedicated hub for an in-depth look at social inequalities in healthcare and what we can do to correct them.
Black Americans are twice as likely to get inadequate sleep
An established study highlights racial differences 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 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 black respondents were consistently more likely to sleep very briefly or briefly during this period compared to their white colleagues.
The team defined very short sleep as less than 5 hours per 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 a night. In comparison, 4.0% of respondents with black people said they slept very briefly and 33.7% said they slept briefly.
These findings, the researchers said, were consistent with those of previous studies, which show that black adults were almost twice as likely to sleep less than 7 hours a night compared to white adults.
Racial differences exist not only in the amount of sleep, but also in the quality or “architecture” of sleep. Some studies have found that African Americans tend not to spend as much time in deep, slow sleep as white Americans and are therefore more likely to report physical exhaustion.
The relationship was mediated through perceived discrimination, which means:
“People who said they had experienced more discrimination had less [deep] sleep in stage 4 and reported that they experienced greater physical exhaustion.”
— Kamala S. Thomas et al.
Sleep-related health outcomes
Prof. Jean-Louis and colleagues write: “Black short sleepers may be at better risk of harmful physiological and hormonal effects of inadequate sleep, which may predispose them to adverse cardiometabolic outcomes.”
In fact, numerous studies and experiments on sleep restrictions have shown a strong link between sleep disorders, obesity, and cardiovascular disease.
Research shows that poor sleep disrupts many metabolic pathways, “leading to more insulin resistance, possibly lower energy consumption, increased appetite, and immunological changes.”
When zooming immunological signaling pathways in particular, several studies have found elevated plasma levels of an inflammation-promoting cytokine called interleukin 6 after partial and complete loss of sleep.
Proinflammatory cytokines such as interleukin 6 have in turn been associated with a higher risk of cardiovascular disease diabetes.
Therefore, sleep deprivation, which is more common among black adults, may well be responsible for some chronic conditions — such as high blood pressure, obesity, and diabetes — to which this group is more predisposed.
What could explain these disparities?
There are several possible reasons for these disparities.
As Prof. Jean-Louis and the team discover, untreated sleep apnoea may be partly to blame. The condition is far more common among black Americans. For example, one study found 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 differences. However, research has found that most differences disappear when people sleep in controlled environments, such as sleep laboratories.
A meta-analysis of 14 studies, in which a total of more than 4,100 participants took part, examined, for example, sleep efficiency, total sleep time and sleep latency in Africa compared to European Americans. The analysis found that the differences “only existed in community-based studies, but not in studies where participants were examined in a laboratory environment that controlled time in bed.”
This suggests that cultural and social factors could be to blame. Prof. Jean-Louis and colleagues list some of these factors that could explain sleep differences between people of color:
- Urban residence: A study of nearly 33,000 adult participants found that living in the city center was associated with an “increased risk of short sleep and a reduced risk of long sleep” among black and Hispanic adults compared to living in out-of-town areas.
- Work schedule: A report from the Population Reference Bureau shows that black and Latino Americans are disproportionately more likely than white peers to work unconventional work hours — while shift work is known for disrupting sleep.
- Workload: Some studies have found that black immigrants are almost three times more likely than white workers to be exposed to work-related stress, an inequality likely explained by workplace discrimination.
In addition, a “lack of emotional support, perceived discrimination, types of industries and occupations, and a high burden of chronic illnesses” could also explain sleep differences, as Prof. Jean-Louis and colleagues explain.
While the reasons for these sleeping gaps may be somewhat unclear for now, one thing is certain: Race-related sleep gaps disproportionately affect the black population in the USA.
Sleep deprivation contributes to further disparities in chronic conditions by causing more of these diseases, in black people, or by exacerbating them.
“In the context of health equity research, inadequate sleep can be a key factor in understanding diseases that disproportionately burden [black adults]. Regardless of whether sleep time in this population is reduced by lifestyle choices or limited by sleep fragmentation, as is the case with sleep apnea, [black Americans] may be at increased risk of chronic diseases (such as diabetes and cardiovascular disease) due to insufficient sleep diseases).”
— Girardin Jean-Louis et al.