Chest
Volume 86, Issue 6, December 1984, Pages 830-838
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Clinical Investigations
COPD Prevalence in Nonsmokers in High and Low Photochemical Air Pollution Areas

https://doi.org/10.1378/chest.86.6.830Get rights and content

The prevalence of respiratory symptoms, as ascertained by questionnaire, was evaluated in 6,666 nonsmokers who had lived for at least 11 years in either a high photochemical pollution area (4,379 individuals) or a low photochemical pollution area (2,287 individuals). Of these, 5,178 had never smoked, and none was currently smoking. The risk estimate for “definite” COPD, as defined in this study, was 15 percent higher in the high pollution area (p=0.03), after adjusting for sex, age, race, education, occupational exposure, and past smoking history. Past smokers had a risk estimate 22 percent higher than never smokers (p=0.01). Multivariate analysis showed a significant effect of air pollution on the prevalence of “definite” COPD which univariate analysis failed to demonstrate.

Section snippets

Materials and Methods

Such a group of nonsmokers became available through the National Cancer Institute funded Adventist Health Study. This prospective Adventist Health Study enrolled individuals in 36,805 Seventh-day Adventist (SDA) households in California in 1974, to study a wide variety of health effects possibly related to the SDA unique lifestyle. Those individuals enumerated in the census questionnaires who were 25 years or older were mailed a detailed lifestyle questionnaire in August 1976. Annual follow-up

Results

A summary of pertinent responses for selected items of the AHSMOG Respiratory Symptoms and Residence History questionnaire used in these analyses are shown separately for the high and low pollution areas in Table 2. Questions dealing with respiratory symptoms were taken from the standard NHLBI questionnaire. Based on questionnaire responses, patients were classified as having chronic bronchitis, asthma, or emphysema.

Criteria were developed for what would be considered as “definite” chronic

Univariate Analysis

We initially looked at the prevalence rates or respiratory symptoms related to several key factors, without adjusting for covariate effects. Along with the crude prevalence rates, we have included the p values from the simple chi square test as shown in Table 3. There was a significantly greater percentage of “definite” COPD in past smokers vs never smokers (p<0.001). While there was a trend toward increased prevalence of COPD in those with an adverse occupational exposure (as compared to those

Multivariate Analysis

We compared the high and low pollution areas on the distribution of a number of possible confounders. We then removed the effects of these confounders with multivariate analysis. The comparisons are given below.

Table 4 shows the sex-age distribution of the population compared to the 1970 California population according to ten-year age intervals. It can be seen that the AHSMOG population tends to be older than the general California population. This is partially due to the screening criteria of

Discussion

Chronic obstructive pulmonary disease has shown an apparent increase in the United States. In the years 1958 through 1967, the death rate from bronchitis increased 80 percent and from emphysema, 172 percent.11 More recently, during the one year time span from 1979 to 1980, age adjusted death rates for COPD and allied conditions increased 9.5 percent.12

Mortality statistics do not, however, tell the whole story. Chronic obstructive pulmonary disease is noted more for its being a source of

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