(Reuters Health) - Even though almost one in four black people in the U.S. may have moderate to severe sleep apnea, a common nighttime breathing disorder, a new study suggests the vast majority haven’t been diagnosed or treated by a doctor.

Sleep apnea that isn’t properly treated has been linked with excessive daytime sleepiness, heart attacks, heart failure and an increased risk of premature death. Often, patients are prescribed treatment with a mask connected to a machine that provides continuous positive airway pressure (CPAP) to keep the airway open at night.

For the study, researchers examined data from the larger, long-term Jackson Heart Study that includes more than 5,000 African American adults in Mississippi. The study team analyzed records for 852 people who had undergone home-based sleep studies. They were 63 years old, on average. Overall, 24 percent were found to have apnea based on the sleep study results.

But less than 5 percent of the people found to have sleep apnea reported being diagnosed or treated for the condition, the study found.

“This is very important because it shows how many people are affected by sleep apnea, but unaware,” lead study author Dayna Johnson of the Rollins School of Public Health at Emory University in Atlanta said by email.

“This finding also supports the importance of screening high-risk individuals for sleep apnea,” Johnson, who led the study when she was at Brigham and Women’s Hospital and Harvard Medical School in Boston.

Most of the study participants were overweight or obese, and the risk of sleep apnea appeared to increase at higher weights, Johnson noted.

However, the study found only about one in five participants reported experiencing excessive daytime sleepiness, a common symptom of apnea that doctors often use to screen for the condition.

This suggests that high-risk patients, including African American people with obesity, may need screening for apnea even when they don’t complain of classic symptoms like sleepiness, Johnson said.

As part of the sleep study, researchers asked participants to wear devices known as actigraphs, which assess nighttime movements and sleep-wake cycles.

People who snored more were more likely to have apnea than participants who didn’t snore, the study found.

But sleepiness and insomnia symptoms didn’t appear to impact whether people had sleep apnea. How long people slept, and what’s known as sleep efficiency, or the amount of time in bed that people spent asleep, also didn’t appear to influence the risk of apnea.

The study wasn’t designed to prove whether or how race or ethnicity might directly affect the risk of apnea or the chances that patients might go undiagnosed.

Another limitation of the study is that it only included people in the Jackson, Mississippi area. The results might be different elsewhere in the country, the researchers note in Circulation.

Even without universal screening for sleep apnea, people with unexplained sleepiness or fatigue should speak to their doctor about being tested for apnea, particularly if they are also obese, said Dr. Timothy Wilt of the University of Minnesota School of Medicine and the Minneapolis VA Center for Chronic Disease Outcomes Research.

“Obesity is a major contributor to obstructive sleep apnea, and obesity rates are high in African American populations and rising in all populations,” Wilt, who wasn’t involved in the study, said by email.

“A healthy life style that includes diet and exercise to achieve ideal body weight (or at least lose weight in obese individuals) is beneficial from a wide range of perspectives,” Wilt added. “It may also reduce the incidence and complications associated with symptomatic obstructive sleep apnea.”

SOURCE: bit.ly/2RrAp1X Sleep, online September 5, 2018.