Airways obstruction, chronic expectoration, and rapid decline of FEV1 in smokers are associated with increased levels of sputum neutrophils

Abstract

Background: Smoking may cause inflammation of the airways and impairment of lung function. To determine the relationship between the type and degree of airways inflammation and the decline in lung function, leucocytes in the sputum of smokers and ex-smokers were examined.

Methods: Forty six smokers and ex-smokers of median age 64 years (25%; 75% percentiles 62;66) with a smoking history of 40.1 (31.7;53) pack years were studied with lung function tests and a questionnaire at the end of a 15 year follow up period. Sputum was induced by inhalation of hypertonic saline and differential leucocyte counts were performed on cytospin preparations.

Results: Adequate sputum samples were obtained in 38 subjects (78%). The ratio of forced expiratory volume in one second (FEV1) to vital capacity (VC) was 67.1 (60; 72)% and the annual decline in FEV1 was 19.4 (12;30) ml/year. Subjects with airways obstruction (FEV1/VC < 63%) had more neutrophils (77 (50;86)%) than those without airways obstruction (60 (43;73)%). The percentage of neutrophils was also significantly greater (77 (62;85)%) in those with chronic expectoration than in those without expectoration (57 (45;75)%. Increased levels of neutrophils in the sputum were correlated with a rapid decline in FEV1 over the 15 year follow up period.

Conclusions: Airways obstruction and chronic expectoration, as well as accelerated decline in lung function, are associated with increased numbers of neutrophils in the sputum of smokers and ex-smokers which suggests that neutrophilic inflammation of the airways may be involved in the pathogenesis of chronic obstructive pulmonary disease.