Adverse Effects of Eosinophilia and Smoking on the Natural History of Newly Diagnosed Chronic Bronchitis

Background: Little is known about risk factors for the progression of disease in individuals with newly developed chronic bronchitis (CB). In addition to the effects of smoking, there was specific clinical and epidemiologic interest in the importance of traits such as eosinophilia and wheezing, more commonly associated with asthma, in the progression of this disease. Methods: We evaluated adult individuals with and without diagnosed CB longitudinally in a representative community population in Tucson, Ariz. These subjects were followed up for 13 years since 1972. Because we were interested in CB specifically, those with diagnoses of emphysema and asthma were removed from the data set. Initial level of FEV1 (%FEV1) and slopes in FEV1were corrected for covariates and other important variables. Results: As expected, persistent and newly diagnosed CB was significantly more common in current and ex-smokers. Furthermore, initial lung function was lower, and decline in FEV1 was steeper in smokers with persistent and newly diagnosed CB. Newly diagnosed cases had steeper declines in FEV1 (–6.84 mL/yr below grand mean of –11.18 mL/yr) than normal subjects (+0.95 mL/yr). The incidence rate of newly diagnosed CB was significantly higher in those with eosinophilia (13.7%) than without eosinophilia (6.7%). Finally, new cases with eosinophilia had similar initial %FEV1(95.4 ± 1%) but much larger declines in function than new cases without eosinophilia: –24.5 versus –16.6 mL/yr. Adverse effects of wheeze were largely explained by smoking and eosinophilia. Conclusion: Eosinophilia is an important aspect of CB in addition to smoking, and it should be considered in its evaluation. The presence of eosinophilia in newly diagnosed CB, with or without wheeze, may warn the clinician of the possibility of a rapid decline in FEV1.