Asthma symptoms often follow a distinct pattern that worsens after sunset, known as nocturnal asthma. Between 30 and 70 percent of people with asthma experience symptoms at least once a month. Nighttime symptoms can range from a persistent cough or mild wheezing to severe exacerbations. Frequent night waking due to asthma is a clear sign that the underlying condition may be poorly controlled.
Internal Factors That Worsen Asthma at Night
The body’s natural 24-hour cycle, or circadian rhythm, plays a significant role in the worsening of asthma symptoms overnight. This internal clock regulates the release of hormones that normally help keep the airways open and suppress inflammation during the day. As the body prepares for sleep, the levels of anti-inflammatory hormones, such as cortisol and epinephrine (adrenaline), naturally decline, often reaching their lowest point around 4:00 AM.
The drop in epinephrine removes its bronchodilating effect, which typically relaxes the muscles around the airways. This hormonal shift leads to increased inflammation and a greater tendency for the bronchial tubes to narrow. Furthermore, the body’s immune response may become more active during the night, contributing to higher levels of inflammatory substances like histamine, which further tighten the airways.
Airway dynamics also change when a person lies flat in a supine position. Lying down shifts the distribution of blood and body fluids, subtly increasing the pressure on the lungs and reducing their overall capacity. This physical change can cause a measurable increase in airway resistance, making it harder to move air in and out of the lungs.
During deep sleep, reflexes that normally protect the airways, such as swallowing and coughing, become less active. This reduced activity allows mucus and secretions to pool in the lower airways and throat, creating an obstruction. The accumulated mucus can irritate the sensitive lining of the airways and trigger a coughing fit or spasm, exacerbating chest tightness and breathlessness.
Sleep Environment and External Triggers
The sleep environment often contains factors that can irritate sensitive airways. Common bedroom allergens like dust mites, pet dander, and mold spores are frequently concentrated in bedding, pillows, and carpets. Dust mites thrive in the warm, humid environment of a bed and release waste products that act as potent asthma triggers, leading to an allergic reaction that peaks hours after initial exposure.
Another condition that frequently co-exists with and exacerbates nocturnal asthma is Gastroesophageal Reflux Disease, or GERD. When a person with GERD lies down, stomach acid can more easily flow back up the esophagus toward the throat. This acid reflux can directly irritate the vagus nerve, which connects the stomach to the lungs, triggering a reflex bronchospasm and airway tightening.
The temperature and quality of the air breathed in during the night can also act as a powerful trigger. Breathing in cold, dry air, often from air conditioning or winter heating systems, causes the airways to lose heat and moisture quickly. This rapid cooling and drying of the bronchial tubes can irritate the sensitive tissue lining, triggering an immediate tightening and spasm of the airways.
Strategies for Reducing Nighttime Symptoms
Adjusting the timing of control medications is a key strategy for managing nocturnal asthma. Long-acting control medications, such as inhaled corticosteroids and long-acting beta agonists, are often scheduled to combat the early morning dip in lung function. Studies suggest that taking a daily inhaled corticosteroid dose in the mid-afternoon, around 4:00 PM, may better suppress the inflammatory cascade that peaks overnight compared to morning dosing.
Lifestyle and environmental adjustments are equally important for mitigating nighttime symptoms. A primary action is to reduce allergen exposure in the sleep space by encasing mattresses, box springs, and pillows in allergen-proof, zippered covers. Bedding should be washed weekly in water that is 130°F (54°C) or hotter to kill dust mites and wash away their irritating allergen. Maintaining a bedroom humidity level below 50% also makes the environment less hospitable for dust mites.
To counteract the effects of gravity and GERD, the head of the bed should be physically elevated by six to eight inches, which is more effective than stacking pillows. For those with reflux, avoiding all food intake for at least three hours before lying down can prevent acid from flowing back into the esophagus. Additionally, trigger foods like caffeine, chocolate, and fatty meals should be limited in the evening.
If a person finds themselves waking up due to asthma symptoms more than twice per month, it suggests that the condition is not adequately controlled and requires medical review. A medical professional can then adjust the dosage of long-term control medications or add a second medication, such as a nighttime leukotriene modifier, to improve stability and prevent the long-term consequences of persistent airway inflammation.