Epidemiology of asthma exacerbations

doi:10.1016/j.jaci.2008.08.003

Journal of Allergy and Clinical Immunology

Volume 122, Issue 4, October 2008, Pages 662-668

https://doi.org/10.1016/j.jaci.2008.08.003 Get rights and content

Exacerbations of asthma sufficient to require urgent medical intervention are often, but not always, associated with viral infection, especially rhinovirus, with significant interaction with allergen sensitization and exposure. Seasonal patterns of exacerbations are seen especially in children, and may be aggravated by lack of adequate maintenance anti-inflammatory drug treatment during the high-risk viral season most well described in the Northern Hemisphere after school return in September. Age and sex differences in the epidemiology of exacerbations remain less than fully explained, but hormonal influences are demonstrable. Frequent exacerbations may be an indication of greater severity of disease, significant comorbidities, or poor compliance with therapy. Recognizing risk factors for exacerbations and implementing appropriate long-term management strategies coupled with improved compliance should reduce morbidity and mortality associated with asthma exacerbations.

Section snippets

Prevalence of exacerbations

Although there has been a gradual decrease in the number of hospital admissions for asthma over the last 2 decades, this may not really reflect a reduction of exacerbations. For economic reasons, there is an increasing reluctance to hospitalize patients and an emphasis on treatment in the emergency department (ED) and discharge home. However, more effective early intervention may be preventing exacerbations from becoming sufficiently severe to warrant hospitalization.⁴

The prevalence rate of

Effects of sex and age

Administrative data from many countries as well as data from carefully conducted epidemiologic studies demonstrate a greater incidence and prevalence of asthma among boys compared with girls before puberty, with more exacerbations requiring hospitalization and ED visits (Table I). At puberty, the sex difference reverses, and until at least midadult life, and likely also thereafter, females have a greater incidence and prevalence of asthma with more exacerbations and hospitalizations.5, 6

Cycles of asthma exacerbations

Anecdotal reports and epidemiologic and clinical studies have long suggested that children frequently experience a worsening of asthma after return to school after the long summer vacation, whereas older adults more frequently have exacerbations associated with the winter season. More precise documentation of these age-related trends has recently been possible using large computer-searchable administrative databases. Johnston and Sears¹¹ examined data obtained through the Canadian Institute for

Etiology of asthma exacerbations

Although much childhood and adult asthma is associated with atopy, the classic notion that the majority of exacerbations in atopic patients with asthma are related to allergen exposure with resultant inflammation has been challenged by a number of studies.²⁰ The availability of monitoring of airway inflammation through measuring cell counts in induced sputum has indicated significant heterogeneity and changing patterns of inflammation during exacerbations, as well as during periods of unstable

Frequent exacerbations

A number of studies have looked at patients with multiple exacerbations. Among Japanese patients with multiple exacerbations despite regular maintenance treatment, there was evidence of substantially increased severity as reflected in use of inhaled and oral corticosteroid therapy, concomitant disease including chronic sinusitis, and intolerance to nonsteroidal anti-inflammatory drugs in comparison with controls.³⁸ Those with multiple exacerbations had persistent air flow limitation and reduced

Severe exacerbations

A small proportion of patients have exacerbations of sufficient severity to be judged life-threatening, and require urgent resuscitative measures including intubation and ventilation until the airway obstruction can be relieved. Factors predicting such severe episodes, generally but not uniformly, include chronic severity with impaired lung function even when maximally treated suggesting chronic airway remodeling from persistent inflammation, and poorly controlled chronic asthma with

Prevention of asthma exacerbations

One of the major problems in long-term management of asthma is the lack of awareness of many patients of the chronic nature of the disease and resultant noncompliance with therapy.⁵⁰ Rather, many believe they have intermittent asthma that is only troublesome when they have overt symptoms, and so they do not continue regular therapy, which has been shown in numerous studies to reduce exacerbations substantially in mild to moderate asthma.51, 52, 53 Many patients believe that asthma comes in

Outcome of exacerbations

Although ED visits and hospitalizations for exacerbations remain relatively common in children and adults, mortality is fortunately rare and is declining.⁷² Nevertheless, mortality is the most serious outcome of an exacerbation. The disparity in mortality rates in different races and social economic groups likely reflects the greater frequency and severity of exacerbations, which in turn reflects less well controlled asthma and less satisfactory long-term care.73, 74 Once the patient is

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Reviews and feature articleEpidemiology of asthma exacerbations

Section snippets

Prevalence of exacerbations

Effects of sex and age

Cycles of asthma exacerbations

Etiology of asthma exacerbations

Frequent exacerbations

Severe exacerbations

Prevention of asthma exacerbations

Outcome of exacerbations

Lancet

J Clin Epidemiol

Chest

Chest

J Allergy Clin Immunol

Ann Allergy Asthma Immunol

Public Health

Aust N Z J Public Health

J Allergy Clin Immunol

Chest

Respir Med

J Allergy Clin Immunol

J Allergy Clin Immunol

J Allergy Clin Immunol

Respir Med

Chest

Respir Med

J Allergy Clin Immunol

J Allergy Clin Immunol

J Allergy Clin Immunol

Chest

J Allergy Clin Immunol

J Allergy Clin Immunol

Lancet

Lancet

Lancet

Lancet

Pulm Pharmacol Ther

Ann Allergy Asthma Immunol

Chest

J Allergy Clin Immunol

Effect of inhaled formoterol and budesonide on exacerbations of asthma

N Engl J Med

A new perspective on concepts of asthma severity and control

Eur Respir J

Trends in asthma hospitalisation: is this related to prevention inhaler usage?

Arch Dis Child

Menopause, postmenopausal estrogen preparations and the risk of adult-onset asthma: a prospective cohort study

Am J Respir Crit Care Med

Prospective study of postmenopausal hormone use and newly diagnosed asthma and chronic obstructive pulmonary disease

Arch Intern Med

Modulation of airway reactivity and peak flow variability in asthmatics receiving the oral contraceptive pill

Am J Respir Crit Care Med

Asthma exacerbations, I: epidemiology

Thorax

The similarities and differences of epidemic cycles of chronic obstructive pulmonary disease and asthma exacerbations

Proc Am Thorac Soc

Reviews and feature article
Epidemiology of asthma exacerbations