Reply to Mehmood: Asthma and Obstructive Sleep Apnea: Taking It to Heart.

From the Authors:

We appreciate the point made by Dr. Mehmood in his letter with regard to our review of the evidence supporting the overlap between asthma and obstructive sleep apnea (OSA) (1). Several reviews on this topic have been published over time, presenting multiple putative pathways whereby asthma and OSA could interact (2–5). Among them, the role of cardiopulmonary interactions in this relationship was brought forward more than a decade ago (2, 4). Since then, much of the evidence has remained at the epidemiologic, database level, as referenced in the letter, with a lack of evidence from well-characterized patients or experimental studies. Furthermore, none of the cited epidemiologic studies that focused on individuals with asthma included OSA in their analyses (6–8), even though objective, standard laboratory-based sleep data were readily available (8). This raises several questions: 1) does OSA independently modulate the interaction of asthma with cardiovascular disease, 2) is there any bidirectionality in the relationship of asthma with cardiovascular disease, and 3) what are the underlying pathways?

The a priori set goal of our review was to focus on mechanisms for which multiple lines of evidence (epidemiologic, clinical, and experimental) have amassed, as detailed for each direction of the relationship (1). Although many other mechanisms (3, 4), including cardiopulmonary interactions, may play a role in the asthma–OSA relationship, in our opinion, the underlying mechanism (or mechanisms) remains to be identified by testing in clinical and experimental studies.