Elsevier

Annals of Epidemiology

Volume 21, Issue 8, August 2011, Pages 615-622
Annals of Epidemiology

Ethnicity and Risk of Hospitalization for Asthma and Chronic Obstructive Pulmonary Disease

https://doi.org/10.1016/j.annepidem.2010.10.015Get rights and content

Purpose

To identify ethnic differences for risk of hospitalization for asthma and chronic obstructive pulmonary disease (COPD).

Methods

We undertook a cohort study with 126,019 participants: 55% whites, 27% blacks, 11% Asians, and 4% Hispanics. To estimate asthma and COPD risk, we used Cox proportional hazards models adjusted for age, sex, body mass index, education, smoking, and alcohol intake. End points were hospitalizations for asthma or COPD.

Results

Compared with whites, relative risks (RR) with 95% confidence intervals (95% CI) for asthma among other groups were: blacks, 1.7 (1.4–2.0); Hispanics, 0.9 (0.6–1.4); and Asians, 1.6 (1.2–2.1). Among Asians, increased risk was concentrated in Filipino men and women and South Asian men. For COPD, whites were at highest risk; RR of blacks was 0.9 (0.7–1.0); Hispanics, 0.6 (0.3– 0.9); and Asians, 0.4 (0.3–0.6). COPD risk among Asians was lowest in Chinese with RR of 0.3 (0.1–0.5).

Conclusions

Ethnic disparities in risk of asthma and COPD as well as between both diseases exist, especially for Asian Americans, who have high asthma risk and low COPD risk. While residual confounding for smoking or other environmental factors could be partially responsible, genetic factors in Asians may be involved in decreased COPD risk.

Introduction

Asthma and chronic obstructive pulmonary disease (COPD) are chronic lung diseases with a high impact on public health and medical expense in the United States. A recent estimate is that asthma affects 23.3 million persons, including 7.0 million children and that 12.1 million American adults suffer from COPD (1). In 2006 there were 444,000 hospitalizations and 3,613 deaths attributed to asthma 2, 3. In the same year COPD caused hospitalization of 672,000 patients and 120,970 deaths, making it the fourth leading cause of death.

Established asthma risk factors include host and environmental traits (4). Host traits that increase risk include genetic predisposition to atopy or airway hyper–responsiveness, obesity, and sex (4). Environmental factors include indoor (e.g., domestic mites, furred animals, fungi, molds, yeasts) and outdoor allergens (pollens, fungi, molds, yeasts), infections, occupational sensitizers, tobacco smoke (passive and active), air pollution, and diet (4). Aside from tobacco smoke, the most important risk factor for COPD, other risk factors include α1–antitrypsin (AAT) deficiency, genetic predisposition, occupational exposures, air pollution, and lower socioeconomic status 5, 6.

In the United States there are racial and ethnic disparities in asthma and COPD prevalence. In 2005, the National Center for Health Statistics reported higher asthma prevalence in black persons and Native Americans, compared with whites (7). Several reports show more hospitalizations and deaths due to asthma in blacks compared with whites 7, 8, 9. Among Hispanics, Puerto Ricans are reported to have higher asthma prevalence than whites (7) and other Hispanic groups (10). Lower asthma rates have been found among Asians, Hawaiians, and Pacific Islanders (11), but there are also reports of a higher risk for Filipinos and South Asian men 12, 13.

COPD rates in whites are higher than in blacks 1, 14. However, there is an increasing trend in hospitalizations, emergency department visits, and mortality of blacks especially women 1, 14. In Hispanics both prevalence and age–adjusted mortality are lower than in whites (1). Data about COPD prevalence among Asian Americans, Pacific Islanders, as well as Native Americans and Alaska Natives are limited, and there is an expressed need for more data (15).

In the present report, we use data about hospitalizations in a large free–living multi–ethnic California population to study ethnic disparities in risk of severe bronchial asthma and COPD.

Section snippets

Subjects and Material

The study protocols were approved by the Institutional Review Board of the Kaiser Permanente Medical Care Program. We studied 126,019 persons who, from 1978 through 1985, voluntarily underwent a health examination offered by a northern California prepaid health plan (16). These persons accounted for more than 80% of all persons who took the examination. Most who failed to complete the examination questionnaire were persons undergoing examination during absences of a special study clerk. The

Asthma

Table 1 provides more detail about baseline traits of the study population, asthma, and COPD groups. Blacks and Filipinos were over–represented in the crude data and the increased risk of these groups was substantiated in the adjusted data (Table 2). All other Asian American ethnic groups had slightly increased risk, so that the RR of all Asians (vs. whites) was similar to that of blacks. The “Other” ethnicity category included many persons of mixed ethnicity, thus containing substantial

Discussion

Our main finding in this analysis was a marked disparity in ethnic relationships between risk of asthma and risk of COPD. White persons were generally at lower risk for asthma but at higher risk for COPD. The greatest ethnic disparity was the lower COPD risk of several Asian ethnic groups compared with that of whites.

Conclusion

Ethnic disparities in risk of asthma and COPD as well as between both diseases exist. Especially notable is the disparity involving Asian Americans, who have high asthma risk and low COPD risk. Residual confounding for smoking or other environmental factors could be partially responsible, but genetic factors in Asians associated with lower prevalence of COPD promoters or to a protective mechanism against the condition may be involved.

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