Minorities don’t sleep as long at night, don’t clock quality zzz’s and are sleepier in the day than their white counterparts, according to a new Northwestern University study presented at the Associated Professional Sleep Societies in Boston and reported by Time.

What’s more, findings showed these sleep differences cannot be fully explained by racial and ethnic disparities in cardiovascular risk factors linked to poor sleep, such as obesity and diabetes.

For the study, researchers from Northwestern University’s Feinberg School of Medicine randomly selected 439 participants from the Chicago phone book. All volunteers were Chicago residents, ages 35 to 64, and of white, black, Hispanic or Asian descent. In addition, scientists screened participants for sleep-specific disorders, such as sleep apnea, a disorder characterized by the regular interruption of a person’s breathing during sleep.

Next, researchers asked participants to wear wrist monitors that have the ability to track the duration and quality of their nighttime sleep.

Findings showed black participants got an average of 6.8 hours of sleep each night compared with 6.9 hours for Latinos and Asians and 7.4 hours for whites in the study. What’s more, when participants were asked to rate the quality of their snooze time, only black participants said they suffered from poor quality sleep. Asian-American participants reported suffering the highest levels of daytime sleepiness.

Because researchers found that racial and ethnic sleep differences persisted even after they adjusted for cardiovascular risk factors, scientists suggested that environmental, social and geographical factors, such as different levels of pollution, noise and crime in certain neighborhoods, might explain why some participants got poor quality sleep.

For those who are missing out on a solid seven to nine hours of quality zzz’s, researchers recommended this simple solution: Engage in a regular calming bedtime routine that includes decreasing screen time with phones, TVs and computers.

Poor quality sleep doesn’t only leave you drowsy. It may also cause you to binge on unhealthy foods. Click here to read why.