Asthma-OSA overlap syndrome: A distinct endophenotype?

Abstract

Purpose: Asthma and obstructive sleep apnea (OSA) are two respiratory diseases that often may coexist, resulting in Alternative Overlap Syndrome (aOVS), which is still underestimated and underdiagnosed.

Objectives: This state-of-art review aims to describe the current evidence on aOVS, including its pathophysiology, clinical, functional and therapeutic implications. A secondary objective is to assess whether aOVS can be identified as a distinct endophenotype needing personalized diagnostic and therapeutic strategies.

Results: Asthma and OSA share several common risk factors, including obesity, gastroesophageal reflux disease (GERD) and rhinitis, which contribute to the pathogenesis of aOVS. From a pathophysiological perspective, aOVS has unique characteristics such as a low arousal threshold, nocturnal bronchial hyperresponsiveness and autonomic nervous system (ANS) dysfunction. These features lead to sleep fragmentation, altered ventilatory control, increased upper and lower airway resistance, and airway and systemic inflammation. From a functional perspective, patients with aOVS present lower FEV₁ and increased nocturnal hypoxemia compared to subjects with only asthma or only OSA. From a clinical perspective, aOVS is linked to reduced asthma control, frequent exacerbations, and a lower quality of life. From a therapeutic perspective, continuous positive airway pressure (CPAP) has a positive impact on asthma control, symptom burden and inflammatory response. Weight loss, GERD and rhinitis management, and emerging therapies such as GLP-1 agonists and biological agents may provide additional benefit.

Conclusions: Current evidence suggests that aOVS may be considered a distinct clinical endophenotype. Its identification is crucial to ensure timely diagnosis, improve management, and direct future research about long-term outcomes and personalized therapy.

Keywords: Alternative overlap syndrome; Asthma; Bronchial asthma; Continuous positive airway pressure; Disorders of excessive somnolence; Obstructive sleep apnea; Polysomnography.