Nocturnal asthma

Presence of asthma symptoms during the night are a known component of the disease. It is still unclear whether night time symptoms are an expression of increased asthma severity or whether nocturnal asthma is a distinct entity. A number of mechanisms have been hypothesized to explain the phenomenon of nocturnal asthma, including exposure to dust mite allergen, late-phase allergic reactions, effects of posture and sleep stage on airway tone, gastro-esophageal reflex, impaired mucociliary clearance, airway cooling, and changes in circadian rhythms of circulating hormones. Several therapeutic options have been studied over the years. These include chronobiological use of corticosteroids, long acting β-agonists, theophylline derivatives and antileukotriene drugs. Correction of comorbidities such as gastro-esophageal reflux disease or sleep apnea may contribute to symptom control in selected cases. Further studies would be useful to better define the underlying mechanisms of nocturnal asthma and response to therapeutic measures.