A recent study demonstrates that asthmatic patients with obstructive sleep apnea (OSA) have a greater decline in lung function (FEV1) over time than those without OSA. The natural history of FEV1 decline in asthmatic patients has been reported to be about 40 ml/year, twice the normal age-related decline. Factors associated with the decline in pulmonary function are age, sex, smoking, acute exacerbations, and obesity.
This is also the first study reporting more exacerbations in asthmatic patients with OSA than in patients without OSA. CPAP treatment, however, can reduce exacerbations in asthmatic patients with OSA. Such exacerbations are also associated with the decline in pulmonary function among asthmatic patients with OSA.
Finally, CPAP treatment was found to alleviate the accelerated decline in FEV1 in asthmatic patients with severe OSA.