Chronic bronchitis is generally considered to be a phenotype of chronic obstructive pulmonary disease (COPD). However, at a Ciba Foundation Symposium in 1958,1 British investigators asserted that, “chronic bronchitis may be present without impairment of lung function.” The significance of nonobstructive chronic bronchitis remains poorly understood. In this issue of JAMA Internal Medicine, Balte et al2 describe lung function and respiratory tract morbidity and mortality longitudinally in a large study that involved data pooled from 5 US general population–based cohorts. The National Heart, Lung, and Blood Institute (NHLBI) Pooled Cohorts Study3 harmonized and pooled data from 9 US epidemiologic cohorts that included spirometric measurements. In 5 of these studies, data on repeated spirometric measurements and respiratory symptoms were collected; these 5 studies form the basis of the study by Balte et al.2 The authors studied 22 325 adults whose spirometric results did not demonstrate airflow obstruction using the usual definition of the ratio of forced expiratory volume in the first second of expiration (FEV1) to forced vital capacity (FVC) of less than 0.70. Among 11 082 ever smokers with 99 869 person-years of follow-up, 2.7% had nonobstructive chronic bronchitis and demonstrated an accelerated decline in FEV1 and FVC, increased risk of chronic lower respiratory tract disease–related hospitalization or mortality, and greater respiratory tract disease–related mortality and all-cause mortality. Among 11 243 never smokers with 120 004 person-years of follow-up, the prevalence of nonobstructive chronic bronchitis was 1.3%, and nonobstructive chronic bronchitis was associated with chronic lower respiratory tract disease–related hospitalization and mortality but not with decline in FEV1:FVC or incident airflow obstruction.
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Woodruff PG, Lazarus SC. Long-term Sequelae of Nonobstructive Chronic Bronchitis—Is Airflow Obstruction Important? JAMA Intern Med. Published online March 02, 2020. doi:10.1001/jamainternmed.2019.7280
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