Airway overlap syndromes with asthma.

The airways, defined as the segment of the respiratory system extending from the pharynx to the alveoli, represent a crucial site for various inflammatory airway diseases. Among the most common are asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis, and obstructive sleep apnea (OSA). Owing to their high individual prevalence, it is not unusual for a single patient to have 2 or more of these conditions simultaneously. Beyond this epidemiologic coincidence, several pathophysiologic links, despite notable differences among the diseases, have been identified. These connections influence not only the mutual prevalence of the disorders but also their clinical management and prognosis, frequently in a bidirectional manner. This constellation of interactions has been termed "overlap syndromes." Overlap syndromes involving asthma are especially frequent, including asthma-COPD overlap syndrome, asthma-OSA overlap syndrome, and asthma-bronchiectasis overlap syndrome. These syndromes often exhibit bidirectional relationships. Asthma, for instance, may aggravate COPD symptoms, prompting modifications in its treatment; it may also worsen preexisting OSA through increased pharynx collapsability, the use of inhaled corticosteroids, or contribute to more frequent bronchiectasis exacerbations. Conversely, the presence of COPD can hinder adequate asthma control, bronchiectasis may enhance the inflammatory burden and exacerbate asthma, and OSA can induce harmful nocturnal oxygen desaturations that impair asthma outcomes. These complex and dynamic interactions underscore the importance of recognizing overlap syndromes in clinical practice. An integrated, individualized approach that considers the coexistence of multiple airway diseases is essential for optimizing diagnosis, therapeutic interventions, and long-term prognosis in affected patients.