MedWire News: Smoking is associated with increased severity of new-onset asthma in allergic adults, research shows.
Writing in the journal Respiratory Research, Riccardo Polosa (University of Catania, Italy) and colleagues observe: "Although factors such as gender, atopy, duration of asthma, bronchial hyperresponsiveness, and frequent asthma exacerbations appear to be important determinants of the severe asthma phenotype, the association between common modifiable risk factors such as cigarette smoking and asthma severity has received surprisingly little attention."
For the current study, the researchers examined the influence of smoking on the severity of new-onset asthma among 371 adults with allergic rhinitis who were followed up for 10 years.
Of the 152 patients who developed asthma during follow up, 74 (48.7%) were current smokers, 17 (11.2%) were former smokers, and 61 (40.1%) had never smoked.
Asthma severity among these patients was calculated according to Global Initiative for Asthma criteria and defined as intermittent, mild persistent, moderate persistent, or severe persistent asthma. For the purposes of this study, patients with moderate persistent or severe persistent asthma were defined as having severe asthma.
Univariate analysis indicated that current and former smokers had a greater risk for severe new-onset asthma than those who had never smoked, at an odds ratio of 2.10, but this became non-significant in multivariate analysis that adjusted for age, gender, family history of atopy, and other factors.
However, pack years of smoking among patients who developed asthma were significantly related to disease severity in multivariate analysis. Indeed, patients with 1-10, 11-20, and more than 20 pack-years of smoking were a respective 1.47, 2.85, and 5.59 times more likely to develop severe asthma than those who had never smoked.
The researchers also found that smokers with asthma had a greater risk for uncontrolled disease than non-smokers who developed the respiratory condition. For example, patients with 1-10 and more than 10 pack-years of smoking were a respective 5.51 and 13.38 times more likely to have uncontrolled asthma than those who had never smoked.
Polosa et al conclude: "Smoking status and smoking duration were markedly related in a dose-dependent fashion to the level of asthma severity and to poor asthma control.
They add: "The demonstration of strong association and clear-cut dose-response relationship of smoking with asthma severity and control is in support of causality."
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