Recovery of bronchial epithelium on stopping smoking.

Bronchial biopsy specimens were studied from 19 patients, comprising five non-smokers, eight current smokers, and six people who had given up smoking between two and 16 years previously. By using a recently developed morphometric technique the structural state of the bronchial epithelium was assessed and described by a score, which specifies the extent to which the epithelial histology departs from the normal, through the changes of mucous-cell hyperplasia and squamous-cell metaplasia. The epithelium was nearer normal in former smokers than current smokers in each of six pairs matched for smoking history. The numerical scale permitted statistical analysis with a precision that is not possible with data based on subjective diagnosis alone: the results of comparing histology with pack-years of cigarette consumption were consistent with the hypothesis that structural recovery occurs in bronchial epithelium in people who stop smoking for over two years.