Asthma and obstructive sleep apnea share a complex, bidirectional relationship that significantly impacts patient quality of life.
The Overlap of Asthma and Obstructive Sleep Apnea
The Centers for Disease Control and Prevention estimates that 21 million adults suffer from asthma in the United States. Economic models from 2013 placed the national cost of asthma at more than 80 billion USD, with projected direct costs reaching 1537 billion USD between 2019 and 2038. Experts note that if all patients achieve asthma control during the next 20 years, 300.6 billion USD—or 20% of direct costs—can be saved.
Alongside these figures, clinical awareness of undiagnosed obstructive sleep apnea has surged. Office visits for OSA grew from 2.0 million in 2000 to 2.7 million in 2010. By 2015, diagnosing and treating OSA in the U.S. cost approximately 12.4 billion USD, while the cost of undiagnosed cases reached an estimated 149.6 billion USD.
Population surveys and meta-analyses document a strong connection between the two conditions. Patients with asthma frequently report sleep fragmentation, nocturnal symptoms, daytime sleepiness, and snoring. Data shows a 2-to-3-times-higher prevalence of obstructive sleep apnea in patients with asthma. Yet, large-scale investigations like the European Sleep Apnea Database study found that only 5% of patients with OSA carried a diagnosis of comorbid asthma, pointing to widespread underdiagnosis or inadequate screening.
Clinical Findings on Disease Severity and Phenotypes
The prevalence of obstructive sleep apnea climbs as asthma severity worsens. Studies show that severe asthma groups experience a higher prevalence of OSA compared to moderate asthma groups, standing at 88% versus 58%. Uncontrolled daytime and nighttime symptoms are also far more common in asthmatics who have comorbid OSA.
Using data from the Wisconsin Sleep Cohort study, researchers reported a higher incidence of OSA in asthmatics with a relative risk of 2.72. They also found that a longer asthma duration, measured in 5-year increments, increased the risk of OSA with a relative risk of 1.07. Despite these upward trends in prevalence, the severity of OSA does not directly correlate with an asthma diagnosis or overall asthma severity.
Diagnostic methods further influence these numbers. Polysomnographic-diagnosed OSA appears frequently in uncontrolled asthma, whereas OSA diagnosed by respiratory polygraphy—which lacks an electroencephalogram—is less common in the same patient groups. Respiratory polygraphy can miss respiratory events involving arousal, leading to underdiagnosis. Furthermore, asthma may lower the threshold for arousal in OSA, resulting in a distinct hypopnea with arousal phenotype. Investigations utilizing esophageal and supraglottic catheters to measure airway resistance have identified increased lower airway resistance and bronchoconstriction episodes during stages 3 and 4 of sleep.
Evaluating Quality of Life and Treatment Control Deficits
Managing asthma effectively requires tracking both physiological benchmarks and patient-reported outcomes. Clinicians typically rely on validated instruments such as the Asthma Control Test and the Asthma Control Questionnaire to capture symptom frequency, rescue medication use, and activity limitation. Quality of life evaluations use specific tools like the Mini-Asthma Quality of Life Questionnaire alongside generic health measures to assess physical, emotional, social, and occupational well-being.
Recent investigations into adult-onset asthma demonstrate that patients with partially controlled or uncontrolled disease score significantly lower across ten out of fifteen domains in generic health-related quality of life instruments. Poorer post-bronchodilator lung function, female sex, and the presence of depression independently associate with a reduced quality of life.
Real-world electronic medical record analyses in the U.S. reveal that one-third of treated asthma patients remain inadequately controlled across all steps of the Global Initiative for Asthma treatment scheme. Control worsens at higher treatment steps, underscoring persistent symptoms despite therapy. Similarly, a cross-sectional multicenter evaluation in Lebanon identified frequent wheezing, sleep disturbances, and psychological distress as key predictors of impairment across physical, emotional, social, and occupational domains, while higher educational attainment emerged as a protective factor.
