Bronchial Asthma: Myths, Controversies, and Dogma

Prepared According to Rubin B. K. Asthma Myths, Controversies, and Dogma. Paediatric Respiratory Reviews. September 6, 2014.

This publication is based on the review article by Professor Bruce K. Rubin, published in Paediatric Respiratory Reviews in 2014. Professor Rubin is affiliated with the Children's Hospital of Virginia Commonwealth University in Richmond, Virginia.

The aim of this article is to present the author's evidence-based perspective, supported by extensive clinical experience and published research, on several widely held beliefs about bronchial asthma.

Asthma Is an Infectious Disease

Whether asthma should be considered an infectious disease remains controversial.

During the 1950s and 1960s, asthma was widely believed to result from chronic bacterial infection and was commonly treated with antibiotics. (1) Although no specific bacterial pathogen was ever identified, clinicians unexpectedly discovered that macrolide antibiotics possess immunomodulatory properties independent of their antimicrobial effects. (2)

Later, attention shifted toward Mycoplasma and Chlamydia species as possible contributors to severe asthma, providing a rationale for macrolide therapy in selected patients. (3) However, clinical studies involving adults with poorly controlled asthma demonstrated clinical improvement regardless of how effectively these microorganisms were eradicated from the airways. (4)

More recently, evidence has emerged suggesting that respiratory infections may contribute to asthma development or exacerbation. Patients with asthma appear to be more susceptible to rhinovirus infections, and human rhinoviruses are now recognized as one of the leading causes of severe asthma exacerbations. (5,6)

The role of respiratory syncytial virus (RSV) remains controversial. A prospective multicenter study conducted at 27 institutions evaluated whether palivizumab could reduce recurrent wheezing in infants born before 36 weeks of gestation, including many with a family history of atopy. Among infants with a positive family history of atopy, palivizumab did not reduce the subsequent development of wheezing compared with untreated infants. These findings suggest that RSV-related wheezing may develop through mechanisms independent of atopy. (7)

Even more intriguing findings have emerged from studies of the respiratory microbiome. It was previously believed that healthy lower airways were sterile, but it is now well established that microorganisms are present throughout the respiratory tract.

Early microbiome studies demonstrated reduced microbial diversity and a higher prevalence of organisms such as Haemophilus species in patients with asthma. (8) However, it remains unclear whether these microbiome changes contribute to asthma development or simply result from the disease itself or its treatment, particularly inhaled corticosteroids (ICS).

Consequently, while current evidence does not support classifying asthma as an infectious disease, ongoing research continues to explore the role of respiratory infections and the airway microbiome in asthma pathogenesis.

Asthma Is an Allergic Disease

More than half of children with asthma also have allergic diseases. Both asthma and allergic disorders are characterized by a T-helper type 2 (Th2)-mediated inflammatory response, and exposure to allergens frequently triggers asthma exacerbations.

Nevertheless, many individuals with asthma—particularly those whose disease begins in adulthood—have no evidence of allergy. (9)

Although allergic diseases undoubtedly influence asthma severity and allergen avoidance or allergy treatment may improve disease control, current evidence does not support considering asthma solely an allergic disease.

Asthma Is Simply Bronchospasm

Bronchial smooth muscle hypertrophy and bronchospasm are characteristic features of asthma, but asthma cannot be explained solely by airway smooth muscle contraction or increased airway hyperresponsiveness.

Bronchodilators are highly effective for relieving acute symptoms and are useful in diagnosing asthma. However, increased airway responsiveness demonstrated by specific challenges (such as allergens) or nonspecific agents (such as methacholine) may also occur in individuals without clinical asthma. (10)

Thus, while bronchospasm is largely responsible for symptoms during an asthma attack, it represents only one component of a much more complex chronic inflammatory disease. (11)

Children Outgrow Asthma

Many parents—and even healthcare professionals—believe that children eventually outgrow asthma.

Because the airways enlarge during growth, particularly in boys during adolescence, asthma symptoms may become less noticeable or even disappear. (12)

However, complete resolution is uncommon in patients with moderate or severe asthma, even among those who respond well to long-term anti-inflammatory treatment. (13)

A more accurate view is that asthma is generally a lifelong condition that can often be successfully controlled, particularly in children requiring long-term anti-inflammatory therapy.

There Is an Asthma Epidemic

Asthma is frequently described as being at epidemic levels, alongside conditions such as gluten intolerance and attention deficit disorders.

However, pediatric pulmonologists regularly encounter both underdiagnosis and overdiagnosis of asthma. (14)

According to Professor Rubin, children with well-controlled, clearly diagnosed asthma rarely require specialist care. In contrast, specialists more commonly see patients whose symptoms remain poorly controlled because of inadequate treatment adherence or those who were incorrectly diagnosed with asthma in the first place. (This observation may not fully apply to Lithuania, where asthma diagnosis generally requires specialist confirmation.)

Current epidemiological evidence does not clearly demonstrate that asthma has reached epidemic proportions. Importantly, asthma-related mortality has declined over the past two decades in many countries, reflecting improvements in diagnosis and treatment. (15)

Studies indicate that approximately 30% of adults previously diagnosed with asthma do not actually have the disease. Misdiagnosis is particularly common among children and older adults. (16)

Asthma is also frequently overdiagnosed in obese individuals—especially men—who seek medical attention because of shortness of breath. (17)

Conversely, asthma is relatively uncommon in children younger than two years. (18) Although many infants experience viral-induced wheezing and are treated with inhaled corticosteroids, this does not necessarily mean they have asthma.

Chronic Cough Is Usually Caused by Asthma

Many children with asthma experience coughing.

Although cough-variant asthma is a recognized phenotype, it is thought to result primarily from excessive mucus production and a relatively poor response to β2-agonist bronchodilators. (19)

Chronic cough as the sole manifestation of asthma is uncommon in children. Studies indicate that fewer than 4% of children with asthma present with cough lasting longer than three weeks as their only symptom. (20)

Shortness of Breath During Exercise Is Always Caused by Asthma

Poorly controlled asthma may certainly cause exercise-induced shortness of breath.

However, according to the author's clinical experience, exercise-induced symptoms are particularly common among athletes who begin vigorous activity without an adequate warm-up. Many of these individuals do not have true asthma and remain symptom-free when properly prepared before exercise.

Despite this, many patients are prescribed short-acting β2-agonists or even inhaled corticosteroids without undergoing appropriate diagnostic evaluation.

In one study, Seear and colleagues assessed 52 children referred because of suspected poorly controlled exercise-induced asthma. Only eight children (15.4%) fulfilled the diagnostic criteria, defined as a decline in forced expiratory volume in one second (FEV₁) exceeding 10% during exercise. Among the remaining participants, 23.1% had poor physical conditioning, 26.9% had vocal cord dysfunction, 13.5% had a cough tic, and 21.1% showed no clinically significant abnormalities. (21)

These findings are consistent with those of Weinberger and colleagues, who demonstrated that children and adolescents complaining of exercise-induced breathlessness most often have poor physical fitness rather than true exercise-induced asthma. (22)

This misconception contributes to another common myth—that children with asthma should limit physical activity.

Current evidence indicates the opposite. The primary goal of asthma treatment is to achieve symptom control sufficient to allow unrestricted participation in physical activity. Regular exercise should be encouraged, as it is beneficial for overall health and should not be unnecessarily restricted in patients with well-controlled asthma.

Allergen-Specific Immunotherapy Is Effective for Treating Asthma

Allergen-specific immunotherapy (AIT) may be administered either subcutaneously or sublingually. Its effectiveness in treating allergic rhinitis is well established.

The evidence supporting its use in asthma, however, is less consistent. Some studies suggest that immunotherapy can reduce asthma symptoms or lower the risk of developing asthma. (23)

Current evidence indicates that allergen-specific immunotherapy may be beneficial for patients whose allergic disease remains inadequately controlled despite medication. However, it remains uncertain whether immunotherapy alone can provide adequate asthma control. Most patients with persistent asthma are still likely to require regular controller medication, even while receiving immunotherapy.

Moving to a Dry Climate Improves Asthma Control

Patients with asthma are sometimes advised to move to regions with a dry climate, while others are encouraged to live near the sea.

In reality, environmental factors are far more complex. Very dry climates generally contain fewer airborne molds, while hot desert regions often have less vegetation and therefore lower pollen exposure. However, these environments may also contain other allergens.

Interestingly, some cities located in desert regions, such as Phoenix, Arizona, have become heavily landscaped and irrigated, creating environments with abundant vegetation despite the surrounding arid climate.

Therefore, simply relocating to a different climate does not guarantee better asthma control.

People With Asthma Cannot Have Pets, or Some Dog Breeds Are Hypoallergenic

Allergic reactions may develop to proteins found in virtually any furry animal.

Interestingly, studies have shown that children exposed to dogs from birth have a lower risk of developing asthma and allergic diseases later in life. (24) This protective effect is no longer observed when a dog is introduced after the child's first year of life. It is thought that early exposure may influence gut microbiome development and immune maturation. (25)

Another common belief is that certain dog breeds are hypoallergenic. For example, in parts of Latin America, a popular myth claims that a child with asthma will improve if the family acquires a Chihuahua because the disease is somehow transferred to the dog.

Although breeds such as poodles are often marketed as hypoallergenic, there is currently no convincing scientific evidence that any dog breed is significantly less allergenic than another. (26)

Long-Term Use of Inhaled Corticosteroids Changes the Course of Asthma

A long-standing hypothesis proposed that prolonged treatment with inhaled corticosteroids (ICS) could suppress airway inflammation sufficiently to prevent airway remodeling and permanently alter the natural course of asthma.

Although ICS remain the most effective medications for long-term asthma control, current evidence does not support the conclusion that they modify the underlying disease process.

Early treatment with inhaled fluticasone in preschool children with recurrent wheezing did not alter the natural history of asthma or recurrent wheezing, nor did it prevent decline in lung function or reduce airway hyperresponsiveness later in life. (27)

Similarly, a large study involving preschool children at high risk of asthma found that two years of ICS treatment did not influence asthma symptoms or lung function during the third year, after treatment had been discontinued. (28)

The author also notes that early corticosteroid exposure may have potential risks. Experimental studies in newborn rhesus macaques demonstrated that inhaled corticosteroids impaired postnatal lung growth and disrupted normal airway and lung tissue development. (29)

Based on current evidence, inhaled corticosteroids effectively control asthma symptoms but do not appear to alter the long-term course of the disease.

Patients Can Become Dependent on Inhaled Corticosteroids

Many patients worry that prolonged use of inhaled corticosteroids may lead to dependence or that the medications will gradually lose their effectiveness.

These concerns may arise from familiarity with medications known to cause dependence, such as opioids or barbiturates.

Healthcare professionals should actively address these misconceptions, as patient education remains an essential component of effective asthma management.

Nebulizers Work Better Than Metered-Dose Inhalers During Severe Asthma Attacks

This issue has been extensively studied. (30–32)

When bronchodilator medications are administered correctly, there is no clinically significant difference in effectiveness between delivery by nebulizer and by metered-dose inhaler. (33)

The main distinction is that nebulizers typically deliver larger medication doses, increasing the risk of systemic adverse effects. (34)

β2-Agonists Improve Mucociliary Clearance

β2-Agonists increase ciliary beat frequency in vivo. However, effective mucociliary clearance depends not only on ciliary movement but also on ciliary strength, epithelial integrity, and the physical properties of airway mucus.

Interestingly, β2-agonists stimulate mucus production in some mammalian species. (35)

Studies by Anderson and Daviskis demonstrated that inhaled β2-agonists do not improve mucociliary clearance in patients with severe asthma. (36)

During an Asthma Exacerbation, Salbutamol Should Always Be Given More Frequently and at Higher Doses

Frequent administration of short-acting β2-agonists is an important component of treating acute asthma exacerbations.

However, excessive dosing increases the risk of adverse effects, including downregulation of β2-receptors, hypokalemia, hyperglycemia, cardiac arrhythmias, tremor, and anxiety.

Clinical studies have shown that continuous administration of very high doses of inhaled β2-agonists provides no significant advantage over appropriately timed intermittent treatment in either children or adults. (37,38)

Professor Rubin notes that asthma deaths resulting from inadequate β2-agonist treatment are uncommon in his institution. In his opinion, bronchodilators are often prescribed more aggressively than is necessary to achieve optimal bronchodilation. He emphasizes, however, that this remains a personal opinion requiring confirmation in randomized clinical trials.

Asthma Phenotypes and Disease Severity Remain Unchanged Throughout Life

Earlier asthma guidelines classified disease severity at the time of diagnosis, implying that this classification remained permanent.

Current understanding has shifted considerably.

Because the primary goal of treatment is to improve asthma control and reduce disease severity over time, assessing severity only at diagnosis has limited clinical value. Modern guidelines determine asthma severity based on the level of treatment required to achieve symptom control. (39)

Asthma phenotypes are likewise dynamic rather than fixed. They may evolve with aging, the development of comorbidities, treatment response, and environmental exposures.

Conclusion

Professor Rubin's review challenges several long-standing assumptions about asthma while emphasizing that medical knowledge continues to evolve. Although many traditional beliefs have been questioned by current evidence, new hypotheses and misconceptions will inevitably emerge as research advances.

Prepared by Laura Malinauskienė, MD
Allergist and Clinical Immunologist
Pulmonology and Allergology Centre, Vilnius University