Nocturnal Asthma (Nighttime Asthma)
Nocturnal Asthma Causes continued...
If you are frequently bothered with heartburn, the reflux of stomach acid up through the esophagus to the larynx may stimulate a bronchial spasm. It's worse when lying down or if you take medications for asthma that relax the valve between the stomach and esophagus. Sometimes, acid from the stomach will irritate the lower esophagus and lead to constriction of your airways. If stomach acid backs up to your throat, it may drip down to the trachea, airways and lungs, leading to a severe reaction. This can involve airway irritation, increased mucus production, and airway tightening. Taking care of GERD and asthma with appropriate medications can often stop nighttime asthma.
Late Phase Response
If you are exposed to an allergen or asthma trigger, the chances are great that airway obstruction or allergic asthma will occur shortly afterward. This acute asthma attack ends within one hour. About 50% of those who experience an immediate reaction also have a second phase of airway obstruction within three to eight hours of exposure to the allergen. This phase is called the late phase response, and it is characterized by an increase in airway responsiveness, development of bronchial inflammation, and a more prolonged period of airway obstruction.
Many studies report that when allergen exposure occurs in the evening instead of in the morning, you are more susceptible to having a late phase response and are more likely to have one of greater severity.
Hormones that circulate in the blood have well‑characterized circadian rhythms that are seen in everybody. Epinephrine is one such hormone, which exerts important influences on the bronchial tubes. This hormone helps keep the muscle in the walls of bronchi relaxed so the airway remains wide. Epinephrine also suppresses the release of other substances, such as histamines, which cause mucus secretion and bronchospasm. Your epinephrine levels and peak expiratory flow rates are lowest at about 4:00 a.m., while histamine levels tend to peak at this same time. This decrease in epinephrine levels may predispose you to nocturnal asthma during sleep.