Asthma in Adults
DescriptionAn in-depth report on how asthma is diagnosed, treated, and managed in adults.
Asthma has dramatically risen worldwide over the past decades, particularly in developed countries, and experts are puzzled over the cause of this increase. The mechanisms that cause asthma are complex and vary among population groups and even from individual to individual. Many asthma sufferers have allergies, and some researchers are targeting common factors in both these conditions. Not all people with allergies have asthma, however, and not all cases of asthma can be explained by allergic response. Other contributing causes need to be studied.
Asthma is most likely to be caused by a convergence of factors that can include genes (probably several) and various environmental and biologic triggers (e.g., infections, dietary patterns, hormonal changes in women, and allergens).
The Allergic Response
Nearly half of adults with asthma have an allergy-related condition, which, in most cases developed first in childhood. (In patients who first develop asthma during adulthood, the allergic response usually does not play a strong causal role, although it may be increasing.) Important irritants or allergens included the following:
The Allergic Process. The allergic process, called atopy, and its connection to asthma is not completely understood. It involves various airborne allergens or other triggers that set off a cascade of events in the immune system leading to inflammation and hyperreactivity in the airways. One description is as follows:
Remodeling and Causes of Persistent Asthma
Over the course of years the repetition of the inflammatory events involved in asthma can cause irreversible structural and functional changes in the airways, a process called remodeling. The remodeled airways are persistently narrow and can cause chronic asthma. Researchers are trying to determine how this process occurs:
Interleukins. Some researchers are looking at potent immune factors, including interleukins 11 and 13. They have been linked to a number of processes possibly involved in remodeling, including overgrowth of cells in the smooth muscles that line the airways and scarring in the airways.
Growth Factors. Compounds known as vascular endothelial growth factor (VEGF) have been observed in the airways of asthma patients. VEGF is a powerful promoter of cell growth in blood vessel linings and some researchers believe it may be major factor in remodeling.
About one-third of all persons with asthma share this condition with another member of their immediate family. Asthma may be more likely to be passed to children from the mother than from the father. Both allergies and asthma are strongly associated with hereditary factors and they share certain genetic markers, but they are not always inherited together.
Research, then, on the genetics of these conditions is confusing and difficult. Of some significant promise, researchers have identified a gene (ADAM33), which has been linked to asthma. The gene regulates one of the enzymes called metalloproteases, which are involved with the smooth muscle in the airway. A mutation of this gene, then, could play a role in airway changes that occur after inflammation.
Hormones or changes in hormone levels appear to play a role in the severity of asthma in women.
Menstrual-Related Asthma. Between 30% and 40% of women with asthma experience fluctuations in severity that are associated with their menstrual cycle. One study indicated that women with menstrually associated asthma tended to have the following characteristics:
Oral contraceptives (OCs) theoretically should help asthma sufferers by leveling out hormonal changes, but they do not appear to have much effect. (There have been a few reports of asthma exacerbation with OCs, but these are uncommon events.)
Asthma during Pregnancy. During pregnancy, one-third of asthmatic women suffer more from the condition, one-third suffer less, and the other third experience no difference in severity. One interesting but unsubstantiated study suggests that expectant asthmatic mothers carrying a female baby tend to have more severe symptoms than do those who are bearing a male.
Menopause and Asthma. Around the time of menopause (called perimenopause) when estrogen declines, the risk for hospitalization in women with asthma increases fourfold compared to previous years. Although it should then follow that hormone replacement therapy (HRT), which contains estrogen, should benefit postmenopausal women studies are inconsistent. As with OCs, if there is an effect one way or the other, it is likely to be weak.
NSAIDs and Acetaminophen
About 10% of asthmatic 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 other NSAIDs, including ibuprofen (Advil) and naproxen (Aleve).
Acetaminophen (e.g., Tylenol) has been the traditional alternative for relief of minor pain for patients who are aspirin-sensitive. Unfortunately, recent evidence has muddied these recommendations. In fact, some asthmatic episodes have been linked to high consumption of acetaminophen among adults.
Experts hope that the new NSAIDs COX-2 inhibitors, which include celecoxib (Celebrex) and rofecoxib (Vioxx), may be safe for AIA. To date, studies are promising but more research is needed to confirm their safety in people with this condition.
Exercise-induced asthma (EIA) is a limited form of asthma in which exercise triggers coughing, wheezing, or shortness of breath.
Asthma occurs primarily at night (called nocturnal asthma) in as many as 75% of asthma patients. 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:
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).
Contributing Medical Conditions
Infections. The role of infections in asthma is complicated. Respiratory infections may play a role in some cases of adult-onset asthma, but may be protective against asthma in small children. (In both children and adults with existing allergic asthma, however, an upper respiratory tract infection often worsens an attack.)
Researchers are particularly interested in the organisms Chlamydiapneumoniae and Mycoplasmapneumoniae adenovirus. They are major causes of both mild and serious respiratory infections and are becoming important suspects in many cases of severe adult asthma. (If such respiratory infections occur in young children, they are unlikely to have any affect on adult-onset asthma.)
In one study, patients whose asthma was initiated after infections had more severe conditions than those whose asthma was due to other causes. The infection-initiated asthma, however, lasted only 5.6 years compared to 13.3 years in the non-infection group.
In any age group, respiratory infections worsen existing asthma in people who have it already. Rhinovirus (the common cold virus) has been reported to be the most common infectious agent associated with asthma attacks. In one study, it was associated with 61% of asthma exacerbations in children and 44% in adults. Some research suggests that colds promote allergic inflammation and increase the intensity of airway responsiveness for weeks.
GERD. At least half of asthmatic patients 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 as follows:
GERD is sometimes hard to detect and might be suspected as a contributor in the following asthmatic patients:
Treating GERD symptoms with anti-acid agents resolves asthma in some (but not all) patients who share both conditions. [See Well-Connected, 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% and 30% of asthmatic patients develop true sinusitis. The presence of sinusitis, however, does not appear to increase the severity of asthma.