People with asthma often find that their symptoms worsen at night. Asthma symptoms such as chest tightness, difficulty breathing, coughing and wheezing interfere with sleep during the night and can cause daytime drowsiness and fatigue. Night-time asthma also makes control of daytime asthma symptoms more difficult. Nocturnal asthma attacks are potentially life-threatening, and studies indicate that asthma-related deaths are more likely to occur at night than during the day.
Nocturnal asthma is associated with several physiological phenomena. Nocturnal levels of nitric oxide, as well as certain cell receptors, decrease at night, resulting in reduced availability of natural bronchodilators. Night-time asthma also is associated with low melatonin levels, as well as low levels of hormones such as epinephrine, which helps keep airways relaxed.
Although these associations are well established, the causes of nocturnal asthma attacks and the reasons why asthma symptoms worsen at night remain unknown. There are several possible explanations. One is that because of the previously mentioned physiological phenomena, airways are more likely to become constricted at night. Another possible trigger is that nasal and lung secretions are more likely to accumulate in the airways and lungs during the night. Decreased lung volume and increased lung pressure from being in a reclining position might result in increased airway constriction. The loss of moisture and heat in airways also are thought to trigger night-time asthma.
People are more likely to experience asthma attacks during the night if they also suffer from gastroesophageal reflux. This condition can exacerbate night-time asthma symptoms, because regurgitated stomach acid sometimes drips into the trachea, causing irritation and airway constriction. People who suffer from both asthma and gastroesophageal reflux often find that nocturnal asthma symptoms reduce in severity or disappear altogether when the reflux is treated effectively.
Nocturnal asthma treatment cannot cure the condition but can help reduce the frequency and severity of night-time asthma attacks. Typical treatment involves tighter control of both daytime and nighttime asthma symptoms with medication. Long-acting medications are most effective, because these continue to provide anti-inflammatory effects during hours of sleep.
Reducing the allergenic potential of the sleep environment also can help prevent night-time asthma. Keeping the bedroom free from dust, pet hair, pet dander and any other known triggers of asthma can reduce nocturnal symptoms. It also can be useful to modify the temperature or moisture content of the air if it is too dry or too cold.