Nocturnal asthma: mechanisms and management.

Nocturnal asthma, defined as an exacerbation of asthma at night, is associated with increases in symptoms and need for medication, increased airway responsiveness and worsening of lung function. Nighttime worsening of asthma has been recognized since the 5th century A.D. and is believed to be quite common, affecting a majority of asthmatics. The mechanisms of nocturnal asthma are intimately related to circadian rhythms, which influence inflammatory cells and mediators, hormone levels and cholinergic tone. Patients with nocturnal asthma symptoms may have greater nighttime activation of inflammatory cells and mediators, lower levels of epinephrine and increased vagal tone. In addition, underlying differences in the glucocorticoid receptor and b- receptors in these patients may diminish their ability to respond to therapy. While sleep appears to play a role in the pathophysiology of nocturnal asthma, it is not essential to it. Selective timing of medication can increase its efficacy and reduce its toxicity. Available therapy includes inhaled and oral corticosteroids, sustained-release theophylline, long-acting b-agonists, leukotriene- modifying agents and anticholinergic medication. The definition, epidemiology, potential mechanisms and management of nocturnal asthma are discussed in this review.