The Relationship Between Sleep and Asthma

Sleep-related asthma, also known as nocturnal asthma, is characterized by a decrease in forced expiratory volume in 1 second of at least 15% between bedtime and wake-up time in patients diagnosed with asthma. In some patients, these decrements in lung function can reach 50%. Nocturnal asthma seems to have significant clinical impact, and the most recent United States guidelines for asthma management emphasize that nocturnal symptoms indicate the need for more aggressive controller therapy. Several factors have been proposed to cause or worsen nocturnal bronchoconstriction, including horizontal posture in bed, airway cooling, exposure to allergens, gastroesophageal reflux, obesity, and obstructive sleep apnea. Several mechanisms of nocturnal bronchial spasm have also been proposed, including circadian fluctuations in hormone levels, circadian variations in autonomic nervous system activity, airway inflammation, and genetic predisposition.