Severe exacerbations predict excess lung function decline in asthma

¹ James Hogg iCapture Centre, St Paul's Hospital, University of British Columbia, Vancouver BC, Canada
² Depts. of Epidemiology
³ Pulmonology, University Medical Center Groningen, University of Groningen, the Netherlands

^* To whom correspondence should be addressed. E-mail: tbai{at}mrl.ubc.ca.

	Abstract

Severe asthma exacerbations are periods of intense airway inflammation that have been hypothesized to contribute to structural changes in the airways. If so, accelerated lung function decline over time should be more prevalent in adult patients with asthma who have frequent exacerbations than those without, but this has not been demonstrated so far.

We performed a cohort study investigating the effect of severe exacerbations on the progression of airway obstruction in 93 non-smoking asthmatics with moderate to severe disease prior to starting inhaled corticosteroids. Subjects were followed for at least 5 years (median follow-up was 11 yrs).

Fifty-six subjects (60.2%) experienced at least one severe exacerbation (median rate 0.10·yr^-1). Oral corticosteroid use and more severe airway obstruction at baseline were associated with a higher exacerbation rate. Independent of these variables, asthma patients with frequent exacerbations had a significantly larger annual decline in FEV₁ (median difference=16.9 mls·yr^-1 (95% CI: 1.5-32.2). Exacerbation rate significantly predicted an excess decline in FEV₁, so that one severe exacerbation per year was associated with a 30.2 ml greater annual decline in FEV₁.

These data support the hypothesis that exacerbations, indicating intermittent periods of worsening airway inflammation, are associated with excess lung function decline in asthma.

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