Airway obstruction in never smokers: results from the Third National Health and Nutrition Examination Survey

Abstract

Purpose: Chronic obstructive pulmonary disease (COPD) is usually described as a disease of cigarette smoking. COPD is rarely considered in persons with no smoking history except in the context of another exposure. Accordingly, the disease has not been well characterized in these "never smokers."

Methods: We evaluated airway obstruction (defined as forced expiratory volume in 1 second/forced vital capacity <0.70) in US adults aged 30 to 80 years interviewed in the Third National Health and Nutrition Examination Survey with valid spirometry who had never smoked. Previously described risk factors were examined for their association with obstruction in bivariate and multivariate analyses.

Results: Never smokers represented 42% of the Third National Health and Nutrition Examination Survey population aged 30 to 80 years, with obstruction prevalence of 91 per 1000. Never smokers accounted for 4.56 million cases of obstruction, or 23% of the total burden. Among these obstructed never smokers, 19% reported a prior diagnosis of asthma alone, and 12.5% reported COPD (alone or with asthma), leaving 68.5% with no prior respiratory diagnosis. After adjustment for other factors, higher rates of obstruction were significantly associated with increasing age, male sex, lower body mass index, and a history of allergies.

Conclusions: Never smokers represent a significant proportion of airway obstruction in US adults. Only one fifth of obstruction in this group is explained by asthma. COPD may explain much of the remainder, although known risk factors were not explanatory in this dataset. Recommendations that lung health screening programs be limited to smokers should be reconsidered.