Common Respiratory Infections Worsen Asthma. Even if the most common respiratory viruses, especially those that cause colds and flus, do not cause asthma in children, they can worsen asthma in children who have it. Rhinovirus, or the common cold virus, for example, has been reported to be the most common infection associated with asthma attacks. In one study, it was associated with 61% of asthma worsening in children. Some research suggests that colds promote inflammation in patients with existing asthma and increase the intensity of airway responsiveness for weeks.
The Hygiene Theory: Early Infections as Protection Against Asthma. An increasingly important theory blames the dramatic increase in asthma on the reductions in childhood infections that have occurred with modern hygiene and antibiotic use. The basic theory rests on the idea that infections stimulate production of specific immune factors called Th1 cells. As these cells build up, they replace other immune factors called Th2 cells, which react to allergens -- a less serious threat to the body. Without infections to stimulate the production of the Th1 infection fighters, the Th2 allergen fighters are not replaced, and they persist at high levels, making the growing child more susceptible to allergies and asthma.
A number of different studies support this theory:
- Some studies suggest that being part of a large family or attending day care increases the risk for early respiratory infections but reduces the risk of childhood asthma. The occasional cold, then, may be protective.
- In one study, researchers measured levels of bacterial byproducts called endotoxins in the mattress dust of 812 children. Those with the highest levels had an 80% lower rates in allergies and asthma.
- Another study further found a strong association between allergy development and the absence of certain beneficial bacteria (called probiotics) carried in the infant's intestines. Infants who were born in more hygienic environments tended to lack these bacteria. Antibiotic overuse and modern hygiene may be reducing these helpful organisms. (Probiotics can be obtained in active yogurt cultures and in supplements, which are being studied for protection.)
The standard vaccinations against serious childhood infections, according to several important studies, pose no risk for asthma. One of the studies even reported some lower risk for asthma and allergies in the second and third years after vaccinations. Infections killed thousands of children every year before immunization became widespread. Asthma, although serious, is rarely fatal in children. No one should stop giving their children vaccinations against childhood killers.
Other Contributing Medical Conditions
GERD. At least half of patients with asthma also have gastroesophageal reflux disease (GERD), the cause of heartburn. It is not entirely clear which condition causes the other or whether they are both due to common factors.
Some theories for the causal connection between GERD and asthma are:
- Acid leaking from the lower esophagus in GERD stimulates the vagus nerve, which runs through the gastrointestinal tract. This stimulated nerve, in turn, triggers the nearby airways in the lung to constrict, causing asthma symptoms.
- Acid back-up that reaches the mouth may be inhaled into the airways (aspirated). Here, the acid triggers a reaction in the airways that cause asthma symptoms.
GERD is sometimes hard to detect and might be suspected as a contributor in the following patients:
- Those who do not respond to asthma treatments.
- Those whose asthma attacks follow episodes of heartburn.
- Those whose attacks are worse after eating or exercise.
- Those whose coughs follow episodes of acid reflux. (One study found that GERD was associated with about half of the episodes of coughs and wheezes in patients with asthma.)
Treating GERD symptoms with anti-acid drugs may resolve asthma in some (but not all) patients who share both conditions. A small 2005 observational study found that while GERD was common in patients with asthma, treatment of GERD had no effect on asthma symptoms. [See In-Depth Report #85, Heartburn and gastroesophageal reflux disease.]
Sinusitis. Almost half of children and adults with allergic asthma have sinus abnormalities, and in various studies, between 17 - 30% of patients with asthma develop true sinusitis. The presence of sinusitis, however, does not appear to increase the severity of asthma.
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Parental Migraines and Childhood Asthma. Some studies have reported a link between childhood asthma and parental migraines, with one small study suggesting that children are about five times more likely to develop asthma if their parents have a history of migraines.
Exercise-Induced Asthma
Exercise-induced asthma (EIA) is a limited form of asthma in which exercise triggers coughing, wheezing, or shortness of breath.
NSAIDs and Acetaminophen
About 10% of adults and some fewer children have aspirin-induced asthma (AIA). With this condition, asthma gets worse when patients take aspirin. Aspirin is one of the drugs known as nonsteroidal anti-inflammatory drugs (NSAIDs). Although aspirin is used to reduce inflammation in other disorders, it appears to have the opposite effect in many asthma cases. It is not wholly known why this occurs. AIA often develops after a viral infection. It is a particularly severe asthmatic condition and is associated with up to 25% of asthma-related hospitalizations. In about 5% of cases, aspirin is responsible for a syndrome that involves multiple attacks of asthma, sinusitis, and nasal congestion. Such patients also often have polyps (small benign growths) in the nasal passages.
Patients with aspirin-induced asthma (AIA) should avoid aspirin and most likely NSAIDs, including ibuprofen (Advil) and naproxen (Aleve).
Acetaminophen (Tylenol) has been the traditional alternative for relief of minor pain for patients who are aspirin-sensitive. Unfortunately, recent evidence has muddied these recommendations. Moreover, some asthmatic episodes have been linked to high consumption of acetaminophen among adults. And a study of children with asthma reported that those who took ibuprofen were less likely to be hospitalized for asthma than those taking acetaminophen. This is of particular concern, since acetaminophen is the pain reliever of choice in small children.
Nocturnal Asthma
Asthma occurs primarily at night (nocturnal asthma) in as many as 75% of patients with the condition. Attacks often occur between 2 and 4 A.M. Factors that might play role in nocturnal asthma may include one or more of the following:
- Chemical and temperature changes in the body during the night that increase inflammation and narrowing of the airways
- Delayed allergic responses from exposure to allergens during the day
- The wearing off of inhaled medications toward the early morning
- An increase in acid reflux (back up of stomach acid) that causes airways to narrow
- Postnasal drip that occurs during sleep
- Conditions relating to sleep, such as sleep apnea or sleeping on one's back, which may worsen any asthma attack that occurs at night
Some experts believe that nocturnal asthma may actually be a unique form of asthma with its own specific biologic mechanisms that occur only at night and which reduce natural steroid hormones (which block inflammation).
Exercise-Induced Asthma (EIA)Exercise-induced asthma (EIA) is a limited form of asthma in which exercise triggers coughing, wheezing, or shortness of breath. This condition generally occurs in children and young adults, most often during intense exercise in cold dry air. Symptoms are generally most intense about 10 minutes after exercising and then gradually resolve. EIA is triggered only by exercise and is distinct from ordinary allergic asthma in that it does not produce a long duration of airway activity, as allergic asthma does. (It should be noted that some people have both forms of asthma.) People who have only EIA do not appear to require long-term maintenance therapy. A study of military recruits with EIA also reported that the condition does not hinder a person's overall physical performance. Medications Cromolyn, a mild anti-inflammatory drug, or short-acting beta2-agonists have been the treatments of choice for preventing EIA. Newer approaches for people who work out regularly include pretreatment with long-acting beta2-agonists, such as salmeterol (Serevent) or the regular use of inhaled corticosteroids. Hints for Reducing EIA EIA occurs only after exercise and is more likely to occur with regular paced activities in cold, dry air. The following are some suggestions for reducing its impact:
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