Sleep disparities: An explainer and research roundup.

On average, humans spend about one-third of their lives sleeping, but the field of sleep medicine is young, dating back to only the 1970s, and research on sleep, particularly disparities in sleep, is still emerging.

Most sleep studies included only white men in the early years and other racial and ethnic groups and women and were not included in studies of sleep disorders until the 1990s, says Dr. Andrea Matsumura, a sleep medicine physician at The Oregon Clinic in Portland, Oregon, and a member of the Public Awareness and Advisory Committee at the American Academy of Sleep Medicine.

But the growing body of literature so far has revealed that sleep plays an important role in human health, and factors beyond an one’s control are linked to sleep problems, which can then affect overall health. Research also shows sleep deficiencies disproportionately impact those who experience other health disparities.

To take into account social, environmental and economic factors affecting sleep, researchers and experts use the term “sleep health” to create a holistic view of sleep.

“When I think about sleep health, I think about the right environment and the right amount of hours for sleep,” says Matsumura. “If the environment is too cold or too warm, or if you don’t have the right bedding, if you’re working three jobs to survive, or if don’t have money for a bed and you’re having to sleep in a chair, that’s going to affect your sleep health, because you’re not going to be able to get enough sleep.”

Sleep disparities

Lack of sleep is associated with chronic conditions such as type 2 diabetes, heart disease, obesity and depression. It can lead to car crashes and mistakes at work, leading to injury and disability. And it’s been associated with early death.

The association between lack of sleep and heart disease has been compelling enough that in 2022 the American Heart Association added sleep to its heart health checklist, along with nicotine exposure, physical activity, diet, weight, blood glucose, cholesterol and blood pressure.

About one-third of U.S. adults reported not getting enough sleep in 2020, according to data from the U.S. Behavioral Risk Factor Surveillance System, a nationally representative telephone survey that collects state-level data about health-related risk behaviors and is run by the Centers for Disease Control and Prevention. That makes for about 35% of adults who sleep less than 7 hours per day, a trend that has remained relatively unchanged since 2013. The CDC recommends 7 or more hours of sleep for adults 18 years and older.

The amount of sleep U.S. adults get varies based on age, sex, state and county of residence, and race and ethnicity.

More 25- to 44-year-olds reported not sleeping enough, compared with other adults, the CDC data shows. Sleep patterns change with age and most of the change happens between young and middle-aged adults and tends remain mostly unchanged in older adults, research shows.

When looking at men and women, slightly more men than women reported lack of sleep in 2020, the CDC data shows. These differences can be driven by menstrual cycles, pregnancy, menopause, and sleep disorders such as insomnia and sleep apnea. For instance, studies show that sleep apnea is more common in men than women, due to factors such as obesity, upper airway anatomy, hormones and aging.

Meanwhile, women tend to report more sleep problems, including inadequate sleep time and insomnia.

Matsumura, who has researched sleep inequities in women, says there’s a psychological component to higher rates of insomnia in women, as they’re more likely to be affected by domestic violence, workplace discrimination, misogyny in workplace and in the world.

“And that weighs heavy on women’s emotional well-being, which then infiltrates into sleep,” she says.

There’s also a delay in diagnosing sleep disorders in women, because oftentimes they’re “explained away,” by health providers, she says.

‘Oh, you have kids. Oh, you’re taking care of parents. Oh, well, your husband’s away at work all the time.’ The classic, stereotypical reasons to explain away women’s symptoms, when in fact, they may actually have a sleep disorder,” Matsumura says. “And there haven’t been enough studies and data to really identify these disparities and really help close the gap.”

Sleep deficiencies also vary by race and ethnicity, the CDC data shows: 31% of white and Asian adults and 32% of Hispanic or Latinos reported that they were not getting enough sleep in 2020, lower than the national average of 35%. In comparison, 38% of American Indian or Alaska Natives, 43% of Black people, and 47% of Native Hawaiian and other Pacific Islanders reported sleeping less than 7 hours per night.

Drivers of sleep disparities

Although there’s been much emphasis on the importance of good sleep habits, sometimes called “sleep hygiene,” many other social and economic factors can override individual efforts.

Research in the past two decades has shown substantial inequities in sleep that parallel other racial, ethnic and socioeconomic disparities in health outcomes.

For instance, studies find that the stress of experiencing of discrimination can disrupt sleep.

A study published in Sleep Medicine in 2015 reviews 17 research papers and finds that discrimination — whether based on race, nationality, religion, gender, sexual orientation or other social factors — is associated with poorer sleep.

The authors of a 2017 review paper published in Population Research and Policy Review, write, “The body’s ongoing anticipation of experiencing racism-related stressors disrupts sleep, a behavior highly responsive to stress reactivity.”

Another study, published in the Journal of Racial and Ethnic Health Disparities in February 2022, finds experiences of discrimination and psychological distress are associated with racial disparities in sleep. “Specifically, Black participants reported more experiences of discrimination, which was associated with greater psychological distress, which was related to poorer sleep health,” the authors write.

One study, published in the Journal of Racial and Ethnic Health Disparities in October 2021, focuses on the role of sleep and fatigue among first-generation Hispanic immigrants. It highlights the importance of understanding how racial discrimination can affect sleep, leading to health declines among Hispanic and Latinx immigrants.

Speaking during a virtual event on sleep hosted in February by the Harvard T.H. Chan School of Public Health, Dr. Carmela Alcántara, an associate professor at Columbia University who studies how discrimination and other stressors affect sleep and health, noted that it’s important to remember that the racial and ethnic disparities are not due to genetic differences, rather it’s the impact of social, economic and environmental factors that can affect sleep.

Buildings, roads, traffic patterns, noise, light pollution, neighborhood safety can disrupt sleep.

“We know for example that marginalized communities, racial/ethnic minorities, are more likely to live in neighborhoods with socioeconomic disadvantage and so that can include neighborhoods that might have higher policing and the influence of greater exposure to noise pollution, or greater exposure to light pollution,” said Alcántara during the Chan School webinar.

Shift work, which refers to a work schedule outside the conventional daytime hours can also affect sleep.

About 16% of the U.S. workers had non-daytime schedules in 2017-2018, including 6% who worked in the evening and 4% who worked at night, according to the Bureau of Labor Statistics.

Local, state and federal policies can also affect sleep.

“Social and health care policies affect financial stress, safety concerns, residential segregation practices, and individual autonomy, which may restrict or facilitate opportunities for achieving good sleep health,” write the authors of a 2020 paper published in Annual Review of Public Health.

Loneliness and social isolation are also associated with poorer sleep health.

Other factors include marital status and level of education. People who are married and have higher levels of education tend to report better sleep health.

“While some of these associations may not be causal, they point to the possibility of higher levels of stress due to everyday challenges encountered by more disadvantaged populations, owing to financial insecurity and less autonomy over their life choices,” write the authors of the Annual Review of Public Health paper.

Also important: Access, and lack of access, to health care.

“It’s access to the medicines for sleep, and access to [continuous] positive airway pressure (CPAP) machines, which cost a lot of money,” says Matsumura.

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