Page 171 - ADULT-ONSET ASTHMA PREDICTORS OF CLINICAL COURSE AND SEVERITY

PART 2 CLINICAL COURSE OF ADULT-ONSET ASTHMA
CONCLUSION AND COMPARISON WITH LITERATURE
Part two of this thesis focused on predictors of the clinical course of adult-onset asthma. Here we showed in Chapter 6 that a considerable propor on of pa ents with new-onset asthma experiences clinical asthma remission a er 5 years. Persistence of the disease can be predicted by the presence of nasal polyps and moderate to severe bronchial hyperresponsiveness. An increase in asthma severity was already observed a er two years of follow-up (Chapter 7). The main risk factor being smoked pack years, in a dose dependent way. Finally, predictors of frequent asthma exacerba ons in smokers and never smokers were blood neutrophils and blood eosinophils respec vely (Chapter 8).
How do our results compare to literature? And what are the di erences compared to childhood onset asthma? The clinical remission rate in our study was higher as compared to previous studies in adult pa ents with asthma, of which only two study speci cally included adult pa ents with new-onset asthma.39, 40 When applying a more stringent de ni on including pathophysiologic remission, the remission rate in our cohort was s ll higher than previously reported.39 One explana on for this di erence might be the rela vely high number of mild asthma pa ents. However, pa ents were included a er referral to secondary and ter ary clinics which means these pa ents would be a good representa on of what clinicians encounter in daily prac ce. Compared to childhood onset asthma the rate of asthma persistence is s ll much higher in adult-onset asthma.41-43 Based on retrospec ve studies the probability of asthma remission in adults decreases when asthma exists for a longer me (> 4 years),42 which suggests that the remission rate in our study is the maximum that can be expected for adult-onset asthma. Epidemiological data also support this hypothesis as an increase of asthma prevalence has been observed with increasing age.44
Presence of nasal polyps was a strong predictor of asthma persistence in our study, which is a novel nding. Other factors associated with remission and persistence of asthma are partly comparable for childhood and adult-onset asthma. In children it has been shown that asthma persistence is strongly linked to greater frequency and severity of asthma symptoms, and more severe airway hyperresponsiveness.45 However, unlike in children, atopic sensi za on was not a predictor of persistence in our study of adults with new onset asthma.46
Increase in asthma severity was already observed in an early stage of the disease which could be predicted by the number of pack years smoked. This was the rst longitudinal study inves ga ng factors associated with an increase in adult-onset asthma severity. Most previous studies were performed in mixed popula ons with childhood and adult-onset asthma pa ents.47-51 One found severe asthma at start of the study as a risk factor for severe disease at follow-up.52 The deleterious e ects of smoking on the prognosis of asthma have been described in several studies. For instance in pa ents with allergic rhini s, who developed
SUMMARY AND GENERAL DISCUSSION
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