Sleep apnea risk linked to asthma control
: Results from a US study suggest that asthma patients at high risk for obstructive sleep apnea (OSA) are more likely to have "not-well-controlled" asthma than those at low risk for the sleep disorder.
Previous studies have suggested that "unrecognized OSA may lead to poor asthma control despite optimal therapy," explain Mihaela Teodorescu (University of Wisconsin School of Medicine and Public Health, Madison) and colleagues.
To investigate further, the team studied 472 patients with asthma, aged 18 to 75 years, who received treatment for their condition at the University of Wisconsin-Madison tertiary-care clinic between 2007 and 2009.
All of the patients completed the Sleep Apnea Scale of the Sleep Disorders Questionnaire (SA-SDQ), which assigns scores on a severity scale of 1-5 for eight OSA symptom items, including loud snoring disruptive to the bed partner, breathing pauses during sleep, and sudden gasping arousals. They also completed the Asthma Control Questionnaire (ACQ), which rates asthma control on a scale of 1.0-7.0, with 1.0 representing adequately controlled asthma.
High risk for OSA was defined by an SA-SDQ score of at least 36 for men and at least 32 for women, and not-well-controlled asthma in both genders was defined by an ACQ score of at least 1.5.
In total, 80 (17%) patients had not-well-controlled asthma, and 109 (23%) were at high risk for OSA.
After accounting for demographic variables and factors known to affect asthma control, such as obesity and gastro-esophageal reflux disease, the researchers found that patients at high risk for OSA were 2.87 times more likely to have not-well-controlled asthma than those at low risk for OSA.
Teodorescu et al conclude in the journal Chest: "These data strengthen the evidence of the role of OSA in asthma control and suggest that OSA may prove to be a treatable target in patients affected by these highly prevalent and interacting conditions."
They add: "Prospective studies with objective sleep assessments are needed if this relationship and its mechanistic basis are to be better understood."
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By Mark Cowen