By Ed Susman, Contributing Writer, MedPage Today
PHILADELPHIA -- Patients with asthma were also more likely to develop obstructive sleep apnea, researchers reported here.
Participants in the Wisconsin Sleep Cohort who self-identified as having asthma at the start of the research in 1988 had a 41% incident obstructive sleep apnea rate, compared with an obstructive sleep apnea incident rate of 29% among participants who did not report asthma at the beginning of the study (P<0.001), said Mihaela Teodorescu, MD, of the University of Wisconsin in Madison.
Of the 205 individuals who reported a history of asthma, 84 developed obstructive sleep apnea during the 8-year interval sleep studies, she reported at the annual meeting of the American Thoracic Society.
Of the 1,278 individuals who entered the study without a self-report of asthma, 369 had developed incident obstructive sleep apnea after 8 years.
"There has been a body of evidence published suggesting that there is a relationship between obstructive sleep apnea and asthma," Teodorescu told MedPage Today. "Each disorder makes the other worse, so understanding what starts this vicious cycle is very important. We asked the question of whether asthma promotes the development of obstructive sleep apnea."
"In this cohort we found that having asthma at baseline predicted an increased incidence of obstructive sleep apnea 8 years later," she said. "Overall, having any asthma at baseline predicted about a 72% higher likelihood of developing obstructive sleep apnea 8 years later."
"Interestingly, when stratifying by the age of diagnosis, childhood onset of asthma was a higher predictor for development of obstructive sleep apnea, with an odds ratio of about 2.1," she said in a press briefing following her poster presentation.
"For each 5 years increment in duration of asthma, the likelihood of developing obstructive sleep apnea increased by 12%," she said.
Susheel Patil, MD, of Johns Hopkins University, who moderated the press briefing, said, "Over the years obstructive sleep apnea has been found not to just be associated with excessive daytime sleepiness but has been associated with other diseases such as cardiovascular outcomes, diabetes and metabolic syndromes."
"I think that the relationship between asthma and obstructive sleep apnea may, indeed, be bidirectional as exhibited in this new study," he told MedPage Today.
Teodorescu explained that in the prospective Wisconsin Sleep Cohort participants are studied every 4 years with laboratory polysomnography, validated questionnaires, and structured interviews.
"We selected people in the cohort who were free of obstructive sleep apnea at baseline," she said. "We stratified them based on their asthma diagnosis which was self-reported and they also self-reported the duration of asthma. We didn't see any differences in obstructive sleep apnea severity when we looked at stratification of asthmatics versus no asthma, but the sample sizes became quite small when we tried to separate these groups."
"Overall we conclude that these prospective data suggest that asthma, particularly of childhood onset may contribute to the development of obstructive sleep apnea later on in life. Childhood asthma onset seems to be more of a risk factor for this disease," she said.
The research into teasing out how the diseases impact each other will require further study, she said. "How intrinsic disease characteristics or associated features starting early in life affect upper airway patency during sleep remains unknown," she said.