Asthma and Obstructive Sleep Apnea Overlap Syndrome Identifies a Phenotype of Sleep Instability and Increased Psychological Burden

Background: The alternative Overlap Syndrome (aOVS), the coexistence of bronchial asthma and Obstructive Sleep Apnea (OSA), represents a distinct clinical phenotype associated with worse clinical outcomes, but little is yet known about its characteristics. We aimed to investigate differences in sleep stability and clinical burden between OSA and aOVS patients matched for age, gender, BMI and Apnea-Hypopnea Index (AHI). Methods: 45 aOVS and 45 OSA patients were compared using demographic, clinical and polysomnographic data. Results: Patients with aOVS exhibited significantly higher odds ratio product (ORP) values for total sleep time (ORPmed: 0.8 ± 0.2 vs. 0.5 ± 0.1, p < 0.001) and Non-Rapid Eye Movement (ORPnr: 0.7 ± 0.3 vs. 0.4 ± 0.1, p < 0.001) sleep compared with OSA patients. Furthermore, patients with aOVS showed a significantly higher risk of developing clinically significant anxiety and fatigue, showing a significantly higher General Anxiety Disorder-7 (GAD-7: 8.7 ± 5.6 vs. 5.7 ± 4.7, p = 0.02) and significantly higher prevalence of fatigue (71% vs. 41%, p = 0.01). These associations remained significant after multivariable adjustment and were independent of OSA severity (AHI). Conclusions: Our findings support the concept that aOVS is characterised by significantly more unstable sleep and a greater psychological burden, even after matching with OSA patients for age, gender, BMI and AHI. Our study also highlights the need to integrate traditional sleep measures with more recent ones, such as ORP, in order to better capture the multidimensional burden of aOVS.