Mild and Moderate-to-Severe COPD in Nonsmokers: Distinct Demographic Profiles

doi:10.1378/chest.128.3.1239

Chest

Volume 128, Issue 3, September 2005, Pages 1239-1244

https://doi.org/10.1378/chest.128.3.1239 Get rights and content

Study objective

To investigate the risk of COPD among nonsmokers.

Design

Case-control study, logistic regression analysis.

Setting

Third National Health and Nutrition Examination Survey, from 1988 to 1994.

Participants

Community residents 18 to 80 years of age, of white, black, or Mexican-American ethnicity. Nonsmokers included never-smokers and former smokers with a < 5 pack-year smoking history who had never smoked cigars or pipes.

Measurements

COPD (FEV₁/FVC < 70%) was classified as mild (FEV₁ ≥ 80% predicted) or moderate to severe (FEV₁ 23 to 79% predicted).

Results

Among 13,995 examinees, 51.3 ± 0.4% were female, mean age was 42.2 ± 0.4 years, 48.7 ± 0.9% were nonsmokers, 8.8 ± 0.3% had mild COPD, and 4.1 ± 0.3% had moderate-to-severe COPD [± SE]. One fourth of mild and moderate-to-severe cases were nonsmokers. Among 7,526 nonsmokers, 4.7 ± 0.3% had mild COPD (n = 403; age, 60.9 ± 1.3 years) and were mostly female (82.5%), while 1.9 ± 0.3% had moderate-to-severe COPD (n = 92, age 39.3 ± 1.3) and were mostly male (88.1%). Few nonsmokers with COPD (12.1 ± 2.4%) had a previous diagnosis of chronic bronchitis or emphysema. Among nonsmokers, physician-diagnosed asthma increased the risk of mild and especially of moderate-to-severe COPD. Independently of asthma, risk of mild COPD in nonsmokers increased with age (doubling every 12 years), before age 60 was lower among men than women, and was inversely associated with current exposure to tobacco smoke at home and at work. In contrast, the risk of moderate-to-severe COPD in nonsmokers was markedly associated with male gender, peaked in middle age, and was inversely associated with nonwhite ethnicity. COPD risks did not vary by minimal smoking history, longest-held occupation, urban residence, income, allergies, thyroid disease, or Helicobacter pylori antibody.

Conclusions

Among nonsmokers, mild and moderate-to-severe COPD are associated with asthma but otherwise have distinct demographic profiles, suggesting that moderate-to-severe disease is not a mere progression of mild COPD.

Section snippets

Spirometry

In the Third National Health and Nutrition Examination Survey (from 1988 to 1994), a representative sample of the civilian, noninstitutionalized population of the United States consented to an interview (assessing demographic characteristics, medical history, medication use, risk behaviors) and a medical examination (including spirometry and a battery of laboratory tests).¹⁰ Spirometry was conducted by a trained technician either in the mobile examination center or in the home of examinees aged

Study Population

Current subjects were white, black, or Mexican-American examinees aged 18 to 80 years whose spirometry findings met the reproducibility and reliability criteria of the American Thoracic Society11, 12 and who provided data on smoking history and height. The upper age limit for the study was chosen to accord with formulas used to derive predicted values of FEV₁ and FVC.¹³

Most of the current analysis was restricted to nonsmokers, a group that included both lifelong nonsmokers of cigarettes,

Definitions

Using a modification of the Global Initiative for Chronic Obstructive Lung Disease criteria, COPD was defined as a FEV₁/FVC < 70% and categorized as mild (FEV₁ ≥ 80% of predicted) or moderate to severe (FEV₁ < 80% predicted).14, 15 Respiratory symptoms (cough or phlegm on most days for > 3 months per year, dyspnea on exertion, or wheezing during the past year) and physician diagnosis of asthma, chronic bronchitis, and/or emphysema were recorded; however, none of these was a current criterion

Statistical Analysis

Sampling weights were taken into account in all analyses (SUDAAN; Research Triangle Institute; Research Triangle Park, NC). Means and percentages were reported with their SEs. Logistic regression analysis was used to identify independent risk factors. Variables found significant (p < 0.05) in univariate analysis were tested in multivariate analysis and retained if they improved the fit of the model. As suggested by published data² and Figure 1, an interaction term for the effect of sex ≥ 60

Study Sample

Of the 16,238 examinees, aged 18 to 80 years and identified as white, black, or Mexican American, 95.4 ± 0.3% underwent spirometry; of these, 95.2 ± 0.3% produced reproducible and reliable results. After excluding 6 persons with acceptable spirometry who lacked data on smoking history or height, eligibility criteria were met by 13,995 examinees, who represented 155.82 million adults nationwide (female gender, 51.3 ± 0.4%; mean age, 42.2 ± 0.4 years). Among this general sample, one half (48.7 ±

Nonsmokers With COPD

The prevalence of mild and moderate-to-severe COPD varied by age and sex (Fig 1). Most nonsmokers (76.1 ± 3.7%) with mild COPD were older (age ≥ 50 years), while most nonsmokers (84.3 ± 5.0%) with moderate-to-severe COPD were younger (age < 50). Women comprised the majority of nonsmokers with mild COPD, but a small minority of those with moderate-to-severe disease (Table 1). The ratio of mild to moderate-to-severe COPD was 1:2 among nonsmoking men but 17.2:1 among nonsmoking women.

The

Nonsmoker Risk of Mild COPD

Univariate associations with thyroid disease, H pylori antibody, education, and ethnicity (Table 1) became nonsignificant after adjustment for age and sex. Instead, multivariate analysis (Table 2) indicated that risk of mild COPD increased with asthma and with age (doubling every 12 years). Risk was reduced among men before age 60 years; thereafter, risk did not differ significantly by sex. Compared to persons without COPD, mild cases were half as likely to be currently exposed to smoking in

Nonsmoker Risk of Moderate-to-Severe COPD

Asthma was even more strongly associated with moderate-to-severe COPD than with mild COPD (Table 2). Unlike mild COPD, the risk of moderate-to-severe COPD was markedly increased among males, peaked in middle age, and was inversely associated with nonwhite ethnicity. Also unlike mild COPD, moderate-to-severe COPD was not associated with current exposure to smoking at home or at work.

Nonrisks for COPD

Neither mild nor moderate-to-severe COPD among nonsmokers was associated with ever smoking up to 5 pack-years (Table 1), occupation involving exposure to airway irritants, urban residence, income, or allergies (data not shown). Associations between COPD and asthma (described above) did not vary by age at asthma diagnosis.

Discussion

According to the current study, nonsmokers account for one fourth (24.9 ± 1.4%) of COPD cases in the United States. Similar proportions of nonsmokers have been reported among COPD cases in the United Kingdom and Spain (22.9% and 23.4%, respectively).9, 18 Few nonsmokers with COPD in the current study had had a previous diagnosis of chronic bronchitis or emphysema. Mild and moderate-to-severe COPD were currently associated with distinct demographic profiles among nonsmokers, suggesting that

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Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).

This work was performed at Pfizer La Jolla Laboratories, San Diego, CA.

Financial support was provided by Pfizer, Inc.

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Chest

Clinical InvestigationsMild and Moderate-to-Severe COPD in Nonsmokers: Distinct Demographic Profiles

Study objective

Design

Setting

Participants

Measurements

Results

Conclusions

Section snippets

Spirometry

Study Population

Definitions

Statistical Analysis

Study Sample

Nonsmokers With COPD

Nonsmoker Risk of Mild COPD

Nonsmoker Risk of Moderate-to-Severe COPD

Nonrisks for COPD

Discussion

Chest

Chest

Am J Med

Chest

Chronic obstructive pulmonary disease: definition and epidemiology

Respir Care

Chronic obstructive pulmonary disease in lifelong nonsmokers: results from NHANES

Am J Public Health

Asthma attacks with eosinophilia predict mortality from chronic obstructive pulmonary disease in a general population sample

Am J Respir Crit Care Med

Effects of environmental tobacco smoke on the respiratory health of adults

Scand J Work Environ Health

Urban air pollution and chronic obstructive pulmonary disease: a review

Eur Respir J

LinkingHelicobacter pyloriand chronic bronchitis: fact or fancy?

J Gastroenterol

Clinical, radiologic, and induced sputum features of chronic obstructive pulmonary disease in nonsmokers: a descriptive study

Am J Respir Crit Care Med

Clinical Investigations
Mild and Moderate-to-Severe COPD in Nonsmokers: Distinct Demographic Profiles