Question: What Is Nocturnal Asthma?
Answer: In nocturnal asthma, FEV1 decreases by at least 15% from bedtime to morning awakening in patients with asthma. In
some patients, the decline in lung function can be significantly more. The decline in lung function is associated with increased hyperresponsiveness of airways and airway inflammation leading to nocturnal symptoms such as cough, wheezing and shortness of breath that disrupt sleep. Patients with large nighttime changes in their FEV1 may also have more daytime symptoms.
Diagnosing Nocturnal Asthma?
The easiest way to diagnose nocturnal asthma is to check a bedtime peak flow and a peak flow on awakening. If there is more than a 15% difference, you have significant nocturnal variability that may be the cause of your symptoms. However, peak flow meters may miss 50% to 80% of nighttime variability in FEV1. Thus, you and your provider may need to consider this and start a therapeutic trial.
Sources:
Sutherland ER. Nocturnal asthma. J Allergy Clin Immunol. 2005 Dec;116(6):1179-86.
Martin RJ. UpToDate. Nocturnal asthma. Accessed April 5, 2009.
