Sleep inequality

“In public health, we focus so much on nutrition and physical activity that we often overlook sleep,” says Dr. Julie Gazmararian, professor of epidemiology. “To me, sleep is the third pillar of health. Sleep has a significant impact on our development, our functioning, and our overall health.”

Like so many other conditions, sleep deficits disproportionately affect the Black community, with about 46 percent of Black Americans failing to get the recommended amount of shut-eye. This variation in sleep may well account for some of the health disparities between races. “We know sleep is critical to good health, and we know African Americans have higher rates of sleep deficits. What we don’t know is why,” says Dr. Dayna Johnson, assistant professor of epidemiology. “Most sleep research is focused on white populations, but there is a clear need to understand the sleep of African Americans. If we can determine why African Americans sleep less, we can perhaps find ways to ameliorate that, and in turn we could make some progress reducing the burdens of diseases like hypertension, diabetes, and heart disease in the Black community.”

Johnson has been studying sleep disparities and sleep deficits for years, looking at how factors like neighborhood social cohesion and the built environment impact sleep. She’s found a strong relationship between the neighborhood environment and sleep. In unsafe, loud, and dense neighborhoods, everyone—regardless of race—tends to sleep poorly. However, when taking a closer look, she found that Black adults were affected most by living in adverse neighborhood environments. 

In addition to the neighborhood environment, she also studies housing and sleep. When studying housing as a marker of socioeconomic status, she found a surprising relationship. The greatest racial disparity in sleep between Black and white adults existed among those in more stable housing (e.g., higher socioeconomic environments), whereas there was little difference in the sleep of Blacks and whites that lived in lower socioeconomic environments.

Another study made a similar discovery looking at race, occupation, and sleep. This study found sleep improved for whites as they climbed the labor ladder—sleep deficits were reported by 35 percent of laborers, 26 percent of support workers, and 25 percent of professionals. Black people charted an opposite trajectory—sleep deficits plagued 35 percent of laborers, 37 percent of support workers, and 40 percent of professionals.

“This is shocking to me,” says Johnson. “You would expect to see a protective effect as you move up the ladder into more affluence and better neighborhoods, but we are not seeing that for African Americans. In fact, we’re seeing the opposite.”

What’s going on? Johnson is not sure, but she has some guesses. “If you are Black in a majority-white neighborhood, you may be more exposed to stressors like discrimination,” she says. “You may respond by consistently working harder to prove yourself, resulting in more accumulated stress.”

In another study, Johnson is moving from looking at the impact of neighborhood factors to that of the home environment. For this, she is enrolling Black people of diverse economic backgrounds in the Atlanta area, but instead of bringing them into a sleep lab—as is common in sleep research—she and her team are going into participants’ homes. “In the lab you are able to get a few other measures, but in the home, we get their actual sleep environment,” says Johnson. “We are not dictating when they go to sleep, they are not in a different bed, and we are able to monitor their sleep in their homes over a 10-day span, so we get more than just a one-night snapshot.” 

She also gets to take a good look at participants’ home sleep environment. She places a monitor in their bedrooms that measures air quality, temperature, humidity, light, and noise. Researchers take an inventory of the bedroom—Are there shades in the windows? TVs and laptops in the room? Do other people or pets share the bed? She then monitors participants’ sleep with a wristwatch-like sensor they wear. 

Johnson did a similar study with data from the Jackson Heart Study, the largest single-site investigation of cardiovascular disease among African Americans. She looked at the bedroom environments (noise, light, temperature) and activities (playing video games, watching TV, eating in bed) of participants, combining various factors into a composite score. She found people with the worst scores slept an astounding 109 minutes less than those with the highest scores. 

The Jackson Heart Study participants were of higher socioeconomic status than most black adults in the United States. Johnson wants to use her current Atlanta study to see how those results may vary along the socioeconomic ladder. 

Building on her theory that stress is a root cause of sleep disparities, Johnson has also launched a clinical trial involving a mindfulness app. Over a six-week span, participants will perform mindfulness exercises before going to bed. Johnson will track their sleep and also compare insulin and stress hormone levels before and after the study via blood draws.

“We’ve known sleep is a problem in the Black community for quite a while, but we’re just now studying the social determinants which are likely contributing to the high burden of poor sleep in this population,” says Johnson. “If we can identify ways to intervene on sleep, maybe we can reduce the burden of poor health outcomes like hypertension and diabetes.”

Story by Martha McKenzie
Designed by Linda Dobson
Photography by Stephen Nowland