Clinical research study
Airway obstruction in never smokers: Results from the Third National Health and Nutrition Examination Survey

https://doi.org/10.1016/j.amjmed.2005.06.041Get rights and content

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.

Section snippets

Study population

The NHANES III was conducted from 1988 to 1994 by the National Center for Health Statistics. By using a stratified multistage clustered probability sample, the survey was designed to identify an unbiased sample that could, using appropriate weights, be extrapolated to the entire civilian noninstitutionalized US population. Study participants completed extensive household and personal health questionnaires and underwent a comprehensive physical examination, including spirometry. A total of 81

Results

Persons who had never smoked made up 42% of the NHANES III population aged 30 to 80 years (Table 1). The total final (crude) study population of never smokers was 4544, representing a weighted study population of 49 993 344 persons. Rates of airway obstruction were 91.2 per 1000 (95% confidence interval: 78.0-104.3) in never smokers, less than half of the rate seen in current and former smokers. There were an estimated 4.56 million persons with no smoking history who had airway obstruction on the

Discussion

This analysis suggests some degree of airway obstruction in more than 9% of US never smokers aged more than 30 years. Less than one fifth of these persons reported a history of asthma alone (ie, without also reporting a diagnosis of emphysema or chronic bronchitis), and another 13% reported a prior diagnosis of COPD, leaving the majority with no reported diagnosis of obstructive respiratory disease.

Our estimates of airway obstruction rates in never smokers are higher than those reported

Acknowledgments

The authors thank Dr. Eva Hnizdo, who provided code for calculating NHANES III industrial categories, and Dr. Jim Thomasson for programming support.

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    This project was supported by Boehringer Ingelheim International GmbH and Pfizer Inc.

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