The ugly consequences of discrimination include a wide array of obvious and straightforward ills, from unequal opportunities at work to personal and state violence.
But more insidious outcomes may also abound, including major threats to health. Research has suggested that people who face discrimination are at increased risk for sleep problems that over time are known to increase risk of other problems, like obesity, diabetes and heart disease.
Now a new study adds more evidence, finding that people who reported experiencing more discrimination (of any kind) spent more time awake throughout the night, and took longer to initially fall asleep, than people who reported experiencing less discrimination. And those who reported facing the most discrimination were twice as likely to report having trouble sleeping as the people who reported facing the least discrimination.
"We know sleep is very important to our overall health and wellbeing," study co-author Haslyn Hunte, assistant professor in the Department of Social and Behavioral Sciences in the School of Public Health at West Virginia University, told The Huffington Post in an email. "In our study, discrimination was a predictor of adverse sleep."
Previous studies have suggested sleep troubles may be more common in people who face discrimination. But this study is the first to use both subjective and objective measures to show it, Hunte said.
Discrimination is linked to poor sleep quality and quantity
The researchers analyzed data from a national survey of 361 adults about perceived discrimination and self-reported measures of sleep. Discrimination was measured in terms of how often the participants reported being treated with less courtesy or respect than others, receiving poorer service than others or feeling threatened or harassed, among other measures.
Sleep was measured in terms of a 19-question survey that everyone in the study completed, as well as by activity trackers the participants wore for a week that recorded how long everyone slept, how long it took participants to fall asleep and how much time everyone spent awake throughout the night.
(The survey data was collected as part of the larger Midlife in the United States national longitudinal study, which was developed to better understand how behavioral, psychological and social factors affect health and well-being as Americans age. Even though self-reported measures of discrimination are vulnerable to reporting error, the data in this survey does represent a large, racially diverse sample, as the researchers explain.)
The people who reported facing more discrimination had 12 percent higher odds of having poor sleep efficiency ― the ratio of time spent asleep to total time spent in bed ― as measured by the activity trackers.
The activity tracker data also showed that people who reported facing the most discrimination took seven minutes longer on average to fall asleep, and spent 11 more minutes awake throughout the night, than the people who reported facing the least discrimination.
Overall, the individuals who experienced the highest levels of discrimination were twice as likely to report experiencing a sleep problem ― like having trouble falling asleep, waking up more often during the night, waking up earlier than they intended to in the morning or having poor-quality sleep ― as the people who reported experiencing the lowest levels of discrimination.
We have all had a night or two where we don't sleep as well. But as one can imagine, the differences noted in this study can become very meaningful over the course of the weeks and months. Haslyn Hunte, West Virginia University
"We have all had a night or two where we don't sleep as well," Hunte said. "But as one can imagine, the differences noted in this study can become very meaningful over the course of the weeks and months [for] these individuals."
The study included people of all races and genders. No single type of discrimination was specified for the study, Hunte said ― discrimination based on race, age, gender and other factors was all considered.
Poor sleep can lead to many other damaging health outcomes
It's worth noting that this study only shows a correlation between facing discrimination and having more trouble sleeping. It doesn't specifically explain what is going on in the brain that causes worse sleep, or rule out other factors that could be contributing to sleep problems, such as the quality of the neighborhood someone lives in. (The study did control for sex, education, age, BMI, diabetes status, smoking status, and having a sleep disorder and other mental health disorders.) The researchers note that additional studies using brain scans could help answer some of those questions.
One hypothesis, though, is that discrimination acts as a psychosocial stressor. Sleep problems are a known physical effect of psychosocial stress (a category that includes work-related stress, marital stress, and stress related to social isolation or one's socioeconomic status, among other things).
Not getting enough sleep, or enough good sleep, is also known to affect stress hormones, blood pressure and other physiological functions in ways that increase risk of chronic health problems, like obesity, diabetes and heart disease. Other studies have found that experiencing discrimination is linked with some of the same effects.
"One proposed mechanism linking discrimination and negative health consequences is through impaired sleep," Hunte said.
This research offers more evidence that clinicians, social workers and others should consider how often people experience discrimination when they look at the stressors in an individual's life ― just like we talk about other stressful life events, like a recent divorce, marriage, birth, death of a loved one or job change, Hunte said.
"It is becoming clear that discrimination is a psychosocial stressor," Hunte said. "And it affects sleep."
Sarah DiGiulio is The Huffington Post's sleep reporter. You can contact her at sarah.digiulio@.