Asthma a Risk Factor for Sleep Apnea?

Asthma may be a risk factor for the development of obstructive sleep apnea, according to the results of a new longitudinal study.

“This is the first study to suggest a causal relationship between asthma and sleep apnea diagnosed with laboratory-based sleep studies,” said Mihaela Teodorescu, MD, MS, Assistant Professor of Medicine at the University of Wisconsin. “Cross-sectional studies have shown that obstructive sleep apnea symptoms/diagnosis are more common among those with asthma, but those studies weren’t designed to address the direction of the relationship.”

The Wisconsin Sleep Cohort Study has been following about 1500 persons, who were aged 30 to 60 years when the study began in 1988. They have completed in-laboratory polysomnography, clinical assessments, and health history questionnaires every 4 years. For the asthma-obstructive sleep apnea study, the researchers focused on 774 enrollees who did not have obstructive sleep apnea when they joined the study and then determined whether sleep apnea developed after 8 years.

Sleep apnea was 1.72 times more likely to develop after 8 years in patients who had asthma. The connection between asthma and obstructive sleep apnea was even stronger among patients who had a diagnosis of asthma as children. Childhood-onset asthma was associated with 2.01 times the likelihood of sleep apnea developing.

Dr Teodorescu and colleagues also found that the duration of asthma affects the chances of sleep apnea developing. For every 5-year increase in asthma duration, the chances of obstructive sleep apnea developing after 8 years increased by 12%.

The study adjusted for variables known to contribute to sleep apnea, including age, sex, body mass index (BMI), smoking, number of alcoholic drinks per week, and nasal congestion. The study also took into account changes in BMI and the addition of new asthma cases.

During the 8-year follow-up period, asthma developed in only 22 patients, and owing to the small sample size, new-onset sleep apnea was not more likely to develop.

If the results of this strong observational study are confirmed by a larger study with more asthma cases, Dr Teodorescu said, the finding would have important clinical relevance.

Dr Teodorescu recommends that primary care physicians “be aware of this relationship and look for obstructive sleep apnea symptoms among patients with asthma. The literature also suggests that obstructive sleep apnea worsens asthma. Treatment for obstructive sleep apnea improves asthma symptoms during the day and night, as well as quality of life and lung function measures. If you identify and treat obstructive sleep apnea early, the hope is that asthma control will improve.”

She added: “Until we get a better understanding of the underlying mechanisms, I suggest screening patients with asthma for obstructive sleep apnea. In the future, as we understand the links between these disorders, we hope to be able to intervene and prevent or mitigate the increased risk of obstructive sleep apnea in asthma and stop this vicious cycle.”

Dr Teodorescu and her colleagues are looking into what leads to obstructive sleep apnea among patients with asthma. “We are working on understanding the mechanism of the relationship,” she said, including focusing on the potential effect of inhaled corticosteroids on upper airway collapsibility.

The researchers presented their results at the American Thoracic Society 2013 meeting.