Asthma

Asthma is a chronic, inflammatory disorder of the airways associated with variable airflow obstruction that reverses either spontaneously or with treatment and bronchial hyper-responsiveness to a range of triggers such as tobacco smoke, cold air, exercise, and strong emotion. It is characterized by recurrent episodes of wheezing, breathlessness, chest tightness, and cough that are usually more pronounced at night and in the early morning.

Asthma Prevalence

Asthma is an increasingly common and chronic disorder that affects the health and quality of life of a considerable number of children and adults worldwide. This disease is estimated to afflict more than 100  million  people  globally;  in  the  United  States, 16 million people (7.5% of the population) report having been diagnosed with asthma, two thirds of whom are younger than 18 years. In 2000, asthma was responsible for 4,487 deaths, 465,000 hospitalizations, and an estimated 1.8 million emergency department visits.

Asthma prevalence, morbidity, and mortality increased exponentially among U.S. adults between 1980  and  1999,  with  a  substantial  75%  increase in prevalence between 1980 and 1994. Asthma prevalence varies by age, gender, and ethnicity. For example, more children than adults have asthma, and among children, more boys than girls have asthma; however, in adolescence, these rates begin to change, although at exactly what point and by what mechanism this change occurs is not known. Compared with males, adult females have higher asthma prevalence rates and higher asthma-related mortality rates. Recent reports suggest that asthma-related mortality rates have been declining since 1996; however, it is also noted that disparities remain between rates for non-Hispanic whites and other ethnic minority groups, particularly African Americans, in regard to asthma related emergency department visits, hospitalizations, and deaths. Several probable factors have been recognized as contributing to these disparities, but identifying interventions to ameliorate their effects has proved more difficult. For example, ethnic minorities are more likely to be poor, uninsured, and undereducated—all factors associated with suboptimal health status, increased morbidity, underutilization of health services, and poorer health outcomes.

Studies have also revealed that asthma is far more common in Western countries than in developing countries; it is more prevalent in English-speaking countries; and as developing countries become more westernized or communities become more urbanized, asthma prevalence increases. These features of asthma prevalence have led to new directions in asthma research other than examining the established risk factors (i.e., allergen exposure and atopy). Recent attention has focused on the interaction between environmental and lifestyle factors in the developed world. For example, the trend toward greater obesity in the developed world has led to a closer scrutiny of an association between asthma and obesity.

In addition, some researchers have begun to examine in utero exposure as well as exposure (or lack of exposure) in the early years that may make an infant susceptible to the development of asthma. Certain issues have emerged as significant in predisposing infants to asthma, such as being born premature, low birth weight, or both, and in utero, as well as postnatal, exposure to tobacco smoke. Research also suggests that a small family size is associated with an increased risk for asthma development. The reason is unclear, but it is suggested that a small family size reduces an infant’s exposure to older siblings, in turn reducing exposure to infections and thereby increasing the risk for atopic disease at older ages.

Another explanation for the increase in prevalence that has garnered a great deal of interest is the “hygiene hypothesis.” The premise is that exposure to naturally occurring infections and microbes essentially immunizes individuals against asthma and other diseases and that reductions in these exposures during the past century, due to the cleaner living of industrialized societies, has led to the increase of allergic diseases such as asthma. Some support for this hypothesis comes from a large U.S. study that found that previous exposure to hepatitis A and herpes simplex virus 1 infections was associated with less asthma, hay fever, and allergen sensitization.

Asthma Development

A summary report from a national survey estimated that 9.3 million annual office visits result in a new, principal diagnosis of asthma, and evidence suggests that a large portion of new diagnoses can be attributable to children. In fact, research indicates that asthma onset occurs early in childhood, often before 2 years of age. Epidemiological studies have suggested that there are several different asthma phenotypes that follow a common final pathway characterized by recurrent airway obstruction. Transient wheezing, one phenotype of asthma, for example, usually resolves by age 3 and is not associated with a family history of asthma or allergic sensitization. Nonatopic asthma, another phenotype, is precipitated by viral infection. Many school-age asthmatic children have been found to have a history of airway obstruction their first 2 to 3 years of life, and in many cases, this obstruction is associated with viral infection. Studies reveal that this infection increases the risk for wheezing up to age 10, but then the risk decreases with age and is no longer significant at age 13.

The third phenotype is atopic asthma. Asthma that begins early in life is often associated with atopy, the genetic predisposition for sensitization to allergens; and allergic sensitization seems to be an important precursor to persistent asthma. Half of the cases of persistent asthma begin before age 3, and 80% begin before age 6; evidence indicates that early onset of symptoms is associated with increased severity of the disease and increased bronchial hyper-responsiveness. Moreover, patients with early-onset asthma also have considerable deficits in lung function growth. Thus, research suggests that mild asthma during childhood may resolve, but in most cases, asthma is a progressive condition, especially in children with a severe form of the disease. These findings highlight the need for early treatment not only to control the often debilitating effects of the disease but also to prevent the irreversible structural lung change or airway remodeling that can lead to permanent airway obstruction.

Asthma Management And Treatment

The  National Asthma  Education  and  Prevention Program (NAEPP) guidelines are considered the gold standard for asthma diagnosis and management. The guidelines recommend a stepped-care model of pharmacotherapy treatment matched to level of asthma severity that should determine successfully managed disease and good health outcomes. There are four levels of asthma severity (mild-intermittent, mild-persistent, moderate-persistent, and severe-persistent) that are distinguished by a combination of factors such as lung function and day and nighttime symptoms. The multiple goals of effective asthma therapy are to prevent chronic and bothersome symptoms such as day or nighttime coughing or breathlessness or exacerbations after exertion, to maintain normal or near-normal lung function, to maintain normal activity levels, and to prevent recurrent exacerbations and reduce the need for emergency department visits or hospitalizations. In addition,  the  patient’s  asthma  should  be  controlled with the least amount of medication necessary, reducing the possibility of adverse effects.

Asthma medications are categorized into two general classes: long-term control medications used to achieve and maintain control of persistent asthma and quick-relief medications used to treat acute symptoms and exacerbations. Current asthma therapy is based on the concept that chronic inflammation is a major feature of asthma. Subsequently, inhaled steroids, the most potent anti-inflammatory asthma medications, have emerged as the cornerstone of the management of persistent asthma, even in young children. There are, however, many medications that can be used at each level of asthma severity, and it is up to the physician to judge the individual patient’s needs and to determine at what step to initiate therapy. The list of medications can be found in the NAEPP guidelines.

Asthma management in children is exceptionally challenging  because  assessment  is  primarily  based on symptoms and pulmonary function cannot be measured reliably in young children and infants. The approach to asthma control is similar, and the same classifications  are  used;  however,  pharmacotherapy can also pose a challenge, given that adequacy of medication delivery is often in question. In addition, there is a limited amount of information on the appropriate dosage of medications for children younger than 5 years; however, recent studies have recognized inhaled corticosteroids as the preferred long-term controller for all levels of persistent asthma in all age groups.

Is There A Cure?

A great deal has been learned in recent years about the pathogenesis and progression of asthma that has  led to new directions in the management of childhood asthma. These directions include the need for early recognition and early intervention with environmental controls and long-term control therapy (inhaled corticosteroids) to prevent adverse effects later in life, but a great deal remains to be learned. It is possible that with the right interventions, the disease could be controlled on a long-term basis and that thus a remission or relative “cure” could be sustained; however, no specific cure as yet has been found for this disease.

References:

1. Beasley, , Crane, J., Lai, C. K. W., & Pearce, N. (2000). Prevalence and etiology of asthma. Journal of Allergy and Clinical Immunology, 105, S466–S472.
2. Centers  for   Disease   Control   and   Prevention.   (2002). Surveillance  for  asthma—United  States,  1980–1999. Surveillance Summaries, 51, 1–13.

3. Centers for Disease Control and Prev (2003). Selfreported asthma prevalence and control among adults— United States, 2001. Morbidity and Mortality Weekly Report, 52, 381–384.
4. Children’s Medical Center of the University of Vir (n.d.). Asthma tutorial. Retrieved from http://www.people. virginia.edu/~smb4v/tutorials/asthma/asthma1.html
5. Martinez, F. D. (2002). Development of wheezing disorders and asthma  in  preschool  children.  Pediatrics,  109,362–367.

6. National Heart,  Lung  and  Blood    (1997).  Expert Panel Report 2: Guidelines for the diagnosis and management of asthma. NIH Publication 97–4051. Bethesda, MD: National Institutes of Health.
7. National Asthma Education and Prevention (2002). Expert Panel Report: Guidelines for the diagnosis and management of  asthma.  Update  on  Selected  Topics—2002. Journal of Allergy Clinical Immunology, 110, S141–S219.
8. Nicolai, T., Pereszlenyiova-Bliznakova, , Illi, S., Reinhardt, D., & von Mutius, E. (2003). Longitudinal follow-up of the changing gender ratio in asthma from childhood to adulthood: Role of delayed manifestation in girls. Pediatric Allergy and Immunology, 14, 280–283.
9. Schmaling, B., Hernandez, D. V., & Giardino, N. D. (2003). Provider and patient adherence with asthma evaluation and treatment. In  T.  N.  Wise  (Series  Ed.)  &  E.  S.  Brown (Vol. Ed.), Advances in psychosomatic medicine: Vol. 24. Asthma: Social and psychological factors and psychosomatic syndromes (pp. 98–114). Dallas, TX: Karger.
10. Skoner, P. (2002). Outcome measures in childhood asthma. Pediatrics, 109, 393–398.
11. Spahn, J. D., & Szefler, S. J. (2002). Childhood asthma: New insights into Journal of Allergy and Clinical Immunology, 109, 3–13.
12. Yawn, P., Wollan, P., Kurland, M., & Scanlon, P. (2002). A longitudinal study of the prevalence of asthma in a community population of school-age children. Journal of Pediatrics, 140, 576–581.