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American Lung Association/American Thoracic Society International Conference
Day 1 - April 25, 1999

Risk Factors for Acute Exacerbations of Symptoms

David Stempel, MD

What places an individual at risk for developing asthma? Which patients are more likely to have acute exacerbations of their asthma? Has there been too much of a focus of late on inflammation in asthma definition and therapy? A series of presentations on asthma risk factors explored these themes.

Of Thunderstorms, Pollen, Smoking and Obesity

Girgis and coworkers[1] from Australia and Lewis and colleagues[2] from the United Kingdom both assessed the association of aeroallergens, thunderstorms and air quality on the occurrence of asthma exacerbations. The Australian study investigated an epidemic of asthma visits during a thunderstorm and found that those patients who were ill during this spring also had evidence of IgE reactivity to rye grass. The use of inhaled corticosteroids protected against flares of illness even in patients with grass pollen reactivity. The complementary English study demonstrated that the thunderstorms tended to enhance the effect of high pollen counts and that this combination might increase asthma morbidity.

Passive cigarette smoke often has been thought to increase the risk of active asthma, but studies to date have not demonstrated this association convincingly. Leitch et al assessed this issue in a questionnaire to more then 7,400 college students[3]. Students newly exposed to passive cigarette smoke had an increased relative risk of wheezing symptoms and awakening with cough than those not exposed. Discontinuation of passive smoke exposure in the previous year was still associated with chest tightness and awakening short of breath, according to the survey. This offers additional evidence of a link between passive cigarette smoke exposure and asthma, although the association does not appear to be as strong as many believe.

Also of interest is whether obesity is a risk factor for asthma or whether active asthma contributes to increasing weight gain. A study by Litonjua and associates demonstrated a weak association between increasing body mass index and the development of bronchial hyperreactivity[4]. But the authors also found that patients with greater bronchial hyperreactivity were more likely over the next three years to significantly increase their body mass. In a slightly different conclusion, Schacter et al reported that patients who were increasingly obese were more likely than those who were not to have a history of recent wheeze and use of asthma medications, but lacked evidence of airway hyerresponsiveness[5]. These two presentations clearly demonstrate obesity's role as both a complication of and complicating factor for recent asthma.

Airflow Obstruction, Inflammation, or Both?

Asthma has commonly been thought of as a disease either of airflow obstruction or inflammation. Now, however, the pendulum seems to be shifting, with the condition increasingly explained has having both of these components.

For example, Toelle and associates reported the results of a 15-year follow-up study that assessed patients for evidence of airway hyperresponsiveness, atopic status, peripheral eosinophils, exhaled nitric oxide (NO) and smoking history[6]. Univariate and multivariate analyses were performed. While multiple factors (atopy, exhaled NO, peripheral eosinophils) were seen as independent predictors of asthma, odds ratios by multivariate analysis increased for recent wheeze only in those patients with evidence of airway hyperresponsiveness and smoking. This supports the concept of the heterogeneity of asthma and suggests that smooth muscle abnormalities may play a significant role in addition to inflammation. Further, it suggests that therapy may need to address both components of the disease.

Several studies demonstrated the greater prevalence of asthma in prepubertal males and higher rates of the condition in post-pubertal women[7]. Adult women tend to frequent the emergency department with symptoms of asthma more than males of the same age. Active cigarette exposure and allergens seem to be additional risk factors. Allergic reactivity to cats appears to be more strongly associated with asthma in smokers and allergic antibody to Alternaria for nonsmokers[8]. Serological evidence of Chlamydia appears to have an association with greater disease severity of asthma[9].

In an attempt to better characterize asthmatics seen in the emergency department, Peters and colleagues looked at the relationship between exacerbation of symptoms and a number of factors[10]. Using multiple regression analysis, the authors found markedly increased odds ratios in patients with extensive sinus disease noted by CT examination, evidence of rhinovirus infection and inflammatory markers of peripheral eosinophilia, and exhaled NO. Several other reports also emphasized the co-morbidity of acute upper respiratory symptoms at the time of presentation to acute care facilities. What remains to be defined is whether the upper respiratory disease is a response to the viral or bacterial infection that simultaneously triggers lower airway reactivity, or whether the extensiveness of the upper airway disease is a direct factor that exacerbates the asthma symptoms.

Eisner and colleagues from Kaiser Northern California assessed the risk of intensive care hospitalization and intubation for asthma[11]. Previous studies have reported that use of more than 5-to-8 canisters of short-acting bronchodilators is associated with increased risk of hospitalization; this risk decreases with the use of inhaled corticosteroids. The California study asked whether these associations also held if one studied patients admitted to intensive care units. This latest report also demonstrated an association between increased risk for severe asthma and overuse of beta agonists, as well as reporting the protective effect of inhaled corticosteroids, providing additional evidence that inhaled corticosteroids are important in decreasing the risks of acute exacerbations of asthma.

Exposure to dog dander is another factor shown to exacerbate symptoms in many asthmatics. As a result, there have been numerous attempts to design a technique to reduce the detrimental effect of exposure to pet hair. Vacuuming the family dog doesn't appear to be the answer, however. British researchers found that this technique offered no protective reduction in dander exposure[12]. Perhaps additional studies will yield more positive results.

References

  1. Girgis S, Marks G, Downs S, et al: Thunderstorm related asthma epidemic in inland New South Wales-Australia: Who is at risk? [Session A39]. ALA/ATS International Conference, San Diego, Ca, 1999.
  2. Lewis SA, Newlands M, Jenner D, et al: Aeroallergens, air pollutants, thunderstorms, and asthma morbidity in derby [Session A39]. ALA/ATS International Conference, San Diego, Ca, 1999.
  3. Leitch DN, Keeley J, Bromly CL, et al: Effect of changes in passive smoke exposure on asthmatic symptoms [Session A39]. ALA/ATS International Conference, San Diego, Ca, 1999.
  4. Litonjua AA, Carey VJ, Sparrow DW, et al: The relationship of body mass index with methacholine airway hyperrresponsiveness in middle-aged to older men [Session A39]. ALA/ATS International Conference, San Diego, Ca, 1999.
  5. Schachter LM, Salome CM, Peat JKA, et al: Obesity is a risk for asthma and wheeze but not airway hyperresponsiveness [Session A39]. ALA/ATS International Conference, San Diego, Ca, 1999.
  6. Toelle BG, Marks GB, Salome C, et al: Hyperresponsiveness and inflammation of the airways are independent predictors of wheeze [Session A39]. ALA/ATS International Conference, San Diego, Ca, 1999.
  7. Mishra A, Schiff MJ, Fein AM, et al: A comparison of demographics of asthma hospital discharges in a large health system with national hospital discharges [Session A40]. ALA/ATS International Conference, San Diego, Ca, 1999.
  8. Soriano JB, Anto, Sunyer J, et al: Relationship of skin test reactivity to decrements in FEV1 in young adults with asthma symptoms [Session A39]. ALA/ATS International Conference, San Diego, Ca, 1999.
  9. Black PN, Scicchitano R, Jenkins C, et al: Chronic infection with chlamydia pneumoniae is related to the severity of asthma [Session A39]. ALA/ATS International Conference, San Diego, Ca, 1999.
  10. Peters EJ, Velez S, Crater S, et al: Chronic infection with chlamydia pneumoniae is related to the severity of asthma [Session A39]. ALA/ATS International Conference, San Diego, Ca, 1999.
  11. Eisner MD, Blanc PD, Chi F, et al: Beta agonists inhaled steroids, and the risk of intensive care unit admission for asthma [Session A40]. ALA/ATS International Conference, San Diego, Ca, 1999.
  12. McGrory H, Custovic A, Craven M, et al: Vacuuming the dog does not reduce dog allergen levels [Session A39]. ALA/ATS International Conference, San Diego, Ca, 1999. References

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