man sleeping with his head on a pillow

Sleep apnea: NHLBI sheds light on an underdiagnosed disorder

Researchers look for biomarkers and genes to speed diagnosis, improve treatment

Mounting scientific evidence about the health dangers of sleep apnea—a common disorder which causes people to stop breathing during sleep—is spurring new and important studies that could lead to improved diagnosis and treatment. Researchers funded by the National, Heart, Lung, and Blood Institute (NHLBI) are sifting through everything from the genetic codes of sleep apnea patients to medications currently on the market, in search of ways to minimize the impact of this potentially deadly disorder.    

Millions of Americans suffer from sleep apnea, but many go undiagnosed and untreated, mainly because some of the telltale symptoms occur during sleep—frequent snoring, gasping for air, silent breathing pauses that can last seconds to minutes. Yet, as NHLBI-funded studies have found, sleep apnea can have severe health consequences over time if left untreated. The disorder has been associated with an increased risk of high blood pressure, heart attack, stroke, obesity, diabetes, and glaucoma. And new findings indicate that pregnant women with sleep apnea have a higher chance of developing high blood pressure and giving birth prematurely. 

The fallout is not just on individuals, but the public at large: because many with the disorder feel persistent sleepiness even after a full night’s sleep, untreated sleep apnea has been associated with lower work performance and a higher risk of accidents on the highway and at job sites. 

“The good news is that several treatments are currently available, and even more are in the pipeline,” said Michael Twery, Ph.D., director of the National Center on Sleep Disorders Research at NHLBI, part of the National Institutes of Health.  But, he added, “a convenient blood test still needs to be developed so that apnea diagnosis is available to all communities and economic groups.”

In recent years, researchers have been scurrying to try to make that happen—and they are looking not just at developing blood tests, but also urine and saliva tests that could be done quickly in a doctor’s office.  “These medical tests are needed to improve the diagnosis of sleep apnea and sleep disorders in general,” Twery said. 

To help accelerate that effort, the NHLBI’s Trans-Omics for Precision Medicine (TOPMed)initiative has been analyzing blood samples from thousands of study volunteers participating in medical research.  Over 2,000 adults with sleep apnea already have been studied in TOPMed. For example, NHLBI-funded researchers have been looking to find new diagnostic markers—clues that indicate the presence of disease—by studying changes in the genetic code, gene expression, and metabolism of those with sleep apnea.  Twery said this line of research discovery is promising. “Potential candidate markers have been found,” he said, “but it’s going to take some time to sort out the best measures.”  

ln the meantime, Twery said, the more familiar people become with the symptoms and dangers of sleep apnea—and what they can do to help minimize their risks—the better off they likely will be.  The Centers for Disease Control and Prevention (CDC) estimates that 50-75 percent of adults with symptoms of sleep apnea have not discussed their condition with a physician.

So, what should the average person know? Here’s a quick primer:

Who’s affected most by sleep apnea? People of all ages, genders, and races suffer from sleep apnea, but African-American males, Asians, Native Americans, and Hispanics appear to have it more, compared to European whites. Excessive weight gain tends to increase the likelihood of getting the disorder, and it affects the severity of the breathing, too. That’s because excessive fat can cause the airway walls to thicken and narrow the inside of the windpipe, making it harder to keep open.  Finally, alcohol, smoking, and certain types of medications, such as opioid pain killers, can interfere with the control of breathing and increase the severity of sleep apnea. 

Are there different kinds of apnea? Yes, there are two main types:  obstructive sleep apnea and central sleep apnea.  Obstructive sleep apnea, the most common, is caused by blockage of the upper airway and results in temporarily impaired airflow during sleep.  This blockage sometimes causes loud snoring, snorting, and gasping, but not everyone who snores has sleep apnea.  Central sleep apnea occurs when the brain fails to send correct signals to your breathing muscles, resulting in breathing stoppage or abnormal breathing patterns.
What should you do if you think you have it? If you have symptoms of sleep apnea, health professionals urge that you see a doctor. If, for example, you get excessively sleepy or fatigued during the day despite getting the recommended seven hours of sleep, and that sleepiness interferes with your daily routine, a doctor could help sort it all out. Based on a medical exam and history, he or she might recommend a sleep study that measures your breathing while you sleep. This can take place either at home or during an overnight visit to a sleep disorders clinic.  These measures can determine whether you have difficulty breathing during sleep and offer clues as to what type of breathing difficulty you have. 

What treatments are currently available to help? No drugs are currently on the market for sleep apnea, but you can take certain steps to help keep the airway open during sleep.  Losing weight, sleeping on your side, and exercising throat muscles can reduce, in some cases, the severity of mild obstructive sleep apnea. In addition, you can use a medical device that delivers slight air pressure through a mask to help keep the airway open during sleep.  These devices are highly effective treatment for the widest range of sleep apnea cases.  

Are there other options? Surgery that widens breathing passages, appliances to open the nose and mouth, and implants that stimulate airway and tongue muscles: All may be recommended by a physician.   NHLBI-supported researchers are building on what has been learned to improve treatment and potentially propose new drug therapies.