Daniel M. Keller, PhD

June 06, 2013

PHILADELPHIA, Pennsylvania — Asthma, especially if it begins in childhood, raises the risk for sleep apnea years later, a new study shows. However, the severity of the obstructive sleep apnea is no different in patients with or without asthma.

"Overall, having any asthma at baseline predicted about a 72% higher likelihood of developing obstructive sleep apnea 8 years later," lead author Mihaela Teodorescu, MD, from the University of Wisconsin at Madison, told Medscape Medical News. "After stratification by age at diagnosis, childhood-onset asthma was a stronger predictor of the development of obstructive sleep apnea."

She presented the study findings here at the American Thoracic Society 2013 International Conference.

It is recognized that obstructive sleep apnea is more prevalent in people with asthma, but it is not clear whether asthma promotes its development.

To address this issue, the researchers conducted a population-based study of subjects from the Wisconsin Sleep Cohort who were 30 to 60 years of age and free of obstructive sleep apnea when they entered the cohort in 1988.

Every 4 years, patients underwent laboratory polysomnography and standardized interviews and completed health questionnaires. They self-reported a physician diagnosis of asthma and age at diagnosis. The outcome was obstructive sleep apnea on polysomnography (apnea–hypopnea index score of at least 5/h or the use of continuous positive airway pressure) 8 years from baseline.

The analysis involved 115 subjects with asthma at baseline and 659 without. At baseline, mean age was about 49 years, nasal congestion or stuffiness was more common in subjects with asthma than without (58% vs 41%; P < .001), and body mass index was slightly higher in subjects with asthma (30.6 vs 28.8 kg/m²; < .001).

Incident obstructive sleep apnea correlated with the presence of asthma. At 8-year follow-up, 3.4% of subjects without asthma at baseline had developed incident asthma. More subjects with asthma at baseline than without developed obstructive sleep apnea (41% vs 29%; P < .001).

Table. Outcome at 8-Year Follow-up

8-Year Outcome Childhood-Onset Asthma Adult-Onset Asthma No Asthma P Value for Any vs No Asthma
Incident obstructive sleep apnea 48% 36% 29% <.001
Apnea–hypopnea index score 5.6/h 5.5/h 4.4/h .005
Continuous positive airway pressure use 0.0% 6.2% 2.0% .039

 

Asthma was an independent risk factor for incident obstructive sleep apnea at 8 years. After controlling for the baseline covariates of sex, age, body mass index, nasal congestion or stuffiness, smoking status, and the number of alcoholic drinks per week, the researchers found that childhood-onset asthma more than doubled the risk for obstructive sleep apnea (odds ratio [OR], 2.16; < .05), and adult-onset asthma increased the risk by more than half (OR, 1.57; < .05).

"The longer the duration of asthma diagnosis, the higher the likelihood of developing obstructive sleep apnea," Dr. Teodorescu reported. "For each 5-year increment in duration of asthma, the likelihood for obstructive sleep apnea increased by 12%."

There was no significant difference in the severity of untreated obstructive sleep apnea when asthma was stratified by age at onset between subjects with and without asthma, but these sample sizes "were quite small," she said.

Dr. Teodorescu recommended that people with asthma be periodically screened, early in life, for sleep disruption, snoring, and other obstructive sleep apnea symptoms, "which could be subtle."

She said that to better understand how asthma increases the risk for obstructive sleep apnea, it will be important to follow childhood cohorts prospectively, "because what happens in the lower airway seems to influence what happens in the upper airway."

"We think the reason for the development of sleep apnea is usually some mechanical problem or anatomical problem with the airway," Susheel Patil, MD, from Johns Hopkins Bayview Medical Center in Baltimore, Maryland, who was not involved in the study, said during a news conference.

"The other possibility is that there is some neural dysfunction or neuromuscular dysfunction of the upper airway. Asthma is kind of interesting to think about as a risk factor for sleep apnea, since we think of asthma as an inflammatory disease," he noted.

Dr. Patil asked about the possibility of inflammation resulting in anatomic abnormalities in the airway or affecting neural function. Dr. Teodorescu said that data are limited in this area, but some experimental biology data suggest that inflammation in the lung leads to changes in the central regulation of breathing control within a few hours.

She added that the main limitation of this study is that when it began in 1988, it depended on self-report of a physician diagnosis of asthma. Nonetheless, the sleep of patients was well characterized with polysomnography.

This study received no commercial funding. Dr. Teodorescu and Dr. Patil have disclosed no relevant financial relationships.

American Thoracic Society (ATS) 2013 International Conference: Poster 213. Presented May 19, 2013.

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