The information in this column can improve your quality of life and even save your life. Apnea refers to absent breathing. Sleep apnea refers to periods of absent breathing during sleep. Obstructive sleep apnea (OSA) is the most common form of sleep apnea, affecting about 18 million Americans, 90 percent of whom are undiagnosed. Most, although not all, people with OSA snore, and often their bed partners notice several seconds of absent breathing followed by a loud snort.