Here’s what sleep doctors say can exacerbate obstructive sleep apnea or put people at risk for the nighttime breathing disorder, according to U.S. News & World Report.

It’s estimated that more than 18 million adults in the U.S. have obstructive sleep apnea, according to the National Sleep Foundation, and for the majority who suffer from the most common form of sleep-disordered breathing, it goes undiagnosed.

Throat muscles, which are usually tense while awake, relax during sleep, allowing the airway to collapse or become plugged by the tongue. As with a kinked hose, the flow stops, sometimes for 10 seconds or more. As the brain senses distress, people may bolt upright and gasp for air, or they may simply snort and go back to sleep, experts say. This can go on hundreds of times a night, without the person realizing it. And it can erode health, says Michael Twery, director of National Center on Sleep Disorders Research within the National Heart, Lung, and Blood Institute.