Asthma, known medically as reactive airway disease, is a chronic lung condition that affects about 20 million Americans, according to the National Heart, Lung, and Blood Institute (NHLBI) at the National Institutes of Health. Symptoms of asthma occur when the airway becomes inflamed and constricts to make breathing difficult. What causes asthma or why incidences of asthma are on the rise is not known, but some have suggested that it could be the result of environmental factors such as an increase in exposure to pollution or indoor allergens. Its increase may also be related to the increase in obesity that is simultaneously occurring. Many researchers are looking for a genetic factor for asthma based on the fact that a person has a higher risk of developing asthma if a member of his or her family has it. Whatever causes asthma, it is a serious and sometimes fatal condition that must be carefully managed.
People with asthma often suffer from nighttime coughing, wheezing and breathlessness that disturb their sleep. It is not clear whether there is a circadian rhythm factor (a circadian rhythm is a rhythm of biological functions occurring in a 24-hour periodic cycle) responsible for these nighttime disturbances or whether sleep in some way contributes to them, but studies designed to uncover the exact influence of sleep or circadian rhythms on asthma have been largely inconclusive. Even so, many researchers believe that asthmatic symptoms are at least partly due to circadian rhythms and use the term "nocturnal asthma" to describe the phenomenon of asthma symptoms worsening at night. Not all asthma sufferers experience nocturnal asthma. Those who do should discuss their symptoms with their doctor in order to develop a treatment plan that addresses the nighttime condition. People with asthma should also be aware that nocturnal asthma is associated with more severe disease and increased mortality.
There are several underlying mechanisms that may shed light on how and why nighttime seems to exacerbate asthma symptoms. First, airway resistance increases throughout the night, whether or not a person sleeps, although the increase is much greater if the person sleeps. Second,