People with asthma are more likely than nonasthmatics to develop obstructive sleep apnea and are roughly three times as likely to develop apnea accompanied by daytime sleepiness, a long-term study finds. The report, in the Jan. 13 JAMA, solidifies a link between the two breathing disorders.
Past studies have linked the two conditions, but apnea is notoriously underreported because it strikes when the individual is asleep. It remains unclear whether asthma can cause sleep apnea.
“This is the first study that has used lab-based data” to identify sleep apnea in people with or without asthma, says study coauthor Mihaela Teodorescu, a pulmonary and critical care physician at the University of Wisconsin–Madison.
Obstructive sleep apnea shortchanges oxygen getting to the brain and disrupts sleep. The Centers for Disease Control and Prevention estimates that 39.5 million people in the United States have been diagnosed with asthma; the National Sleep Foundation estimates that 18 million people in the United States have sleep apnea.
Teodorescu and her colleagues analyzed data from participants in the Wisconsin Sleep Cohort Study, which since 1988 has tracked sleep disorders in adult volunteers who undergo a lab-supervised sleepover session every four years. The team looked at 81 volunteers with preexisting asthma and 466 nonasthmatics who had been in the study for at least four years. The researchers accounted for differences between the groups in sex, age at the start of the study, nasal congestion, smoking status, alcohol consumption and body mass index.
After these adjustments, the risk of developing obstructive sleep apnea during the first four-year period was 39 percent greater in the asthma group, and the risk of developing apnea plus daytime sleepiness was 2.7 times as high. Nearly two-thirds of the volunteers were in the study for more than eight years. When researchers analyzed data from 468 of those people, 49 percent of those who had preexisting asthma developed obstructive sleep apnea compared with 28 percent of the others.
Spotting sleep apnea in regular lab tests eliminates some of the vagaries of self-reported sleep problems and regular visits enable researchers to update information on patients’ BMI and other characteristics, Teodorescu says. Apart from chronic nasal obstruction and obesity, other problems that show up in both asthma and apnea include inflammation in the respiratory system and upper airway collapse, which the new study didn’t measure. Teodorescu says a better understanding of these overlapping factors between asthma and apnea might clarify the links and lead to improved treatments.