Asthma Attacks Among Persons with Current Asthma — United States, 2001–2010

Jeanne E. Moorman, MS

Cara J. Person, MPH

Hatice S. Zahran, MD

Division of Environmental Hazards and Health Effects, National Center for Environmental Health, CDC

Corresponding author: Jeanne Moorman, Division of Environmental Hazards and Health Effects, National Center for Environmental Health, CDC. Telephone: 770-488-3726; E-mail: zva9@cdc.gov.

Introduction

Asthma is a chronic inflammatory disorder of the airways that is characterized by episodic and reversible airflow obstruction, airway hyper-responsiveness, and underlying inflammation. Common asthma symptoms include wheezing, coughing, and shortness of breath (1). With correct treatment and avoidance of exposure to environmental allergens and irritants that are known to exacerbate asthma, the majority of persons who have asthma can expect to achieve optimal symptom control (2).

Multiple reports published previously provide detailed surveillance information on asthma (1,3–8). A 1987 report that included asthma surveillance data for 1965–1984 identified differences among certain demographic groups by age, sex, and race/ethnicity (5). Subsequent asthma surveillance reports confirmed these differences and documented that the differences have persisted over time (1,3,4,6). These reports indicate that population-based asthma prevalence rates, emergency department visit rates, and hospitalization rates were higher among blacks than among whites, higher among females than among males, higher among children (aged 0–17 years) than among adults (aged ≥18 years), and higher among males aged 0–17 years than among females in the same age group. In addition, more detailed analysis of ethnicity data demonstrated that asthma health outcomes differed among Hispanic groups. Hispanics of Puerto Rican descent (origin or ancestry) had higher asthma prevalence and death rates than other Hispanics (e.g., Hispanics of Mexican descent), non-Hispanic blacks, and non-Hispanic whites (7,8).

Current asthma prevalence rates among the demographic groups for the years covered in this report were similar to those in previous CDC reports (1,3,4,6). During 2006–2010, an estimated 8.0% of the U.S. population had current asthma. Asthma prevalence varied by demographic group: 6.9% among males, 9.0% among females, 9.4% among children, 7.6% among adults, 7.9% among whites, 10.5% among blacks, 10.8% among American Indians/Alaska Natives, 5.0% among Asians, 14.4% among multi-race/other-race persons, 15.9% among Puerto Ricans, and 5.4% among Mexicans.

This report is part of the second CDC Health Disparities and Inequalities Report (CHDIR). The 2011 CHDIR (9) was the first CDC report to assess disparities across a wide range of diseases, behavior risk factors, environmental exposures, social determinants, and health-care access. The topic presented in this report is based on criteria that are described in the 2013 CHDIR Introduction (10). This report provides information regarding asthma attacks among persons with current asthma that supplements information about current asthma prevalence provided in the 2011 CHDIR (4). The purposes of this report are to discuss and raise awareness of differences in asthma attacks among persons with current asthma and to prompt actions to reduce these disparities.

Methods

To examine whether disparities in asthma attacks exist among persons with current asthma by selected demographic characteristics, CDC analyzed data from the 2001–2010 National Health Interview Survey (NHIS). NHIS is an annual, in-person survey of the civilian, noninstitutionalized U.S. population based on a multistage sampling of households (11). An adult family member is selected to act as a proxy respondent for children aged 0–17 years. NHIS includes several questions about asthma. The first question, "Have you ever been told by a doctor or other health professional that you had asthma?" has been used as a lifetime prevalence measure for asthma since 1997. A second question, "Do you still have asthma?" was added in 2001. Respondents are considered to have current asthma if they answer "yes" to both of these questions. A response of "yes" to a third question, "During the past 12 months, have you had an episode of asthma or an asthma attack?" indicates an attack in the past year and was used in this analysis as an indicator of symptom control (1,3,4,6).

The percentage of persons with current asthma who reported an asthma attack in the past year, crude prevalence ratios, and adjusted prevalence ratios were estimated for selected demographic characteristics: race/ethnicity, sex, age (children aged 0–17 years, adults aged ≥18 years, and eight age groups), educational attainment for adults, place of birth, geographic region, and federal poverty level (FPL). Estimated percentages with standard errors and prevalence ratios with 95% confidence intervals (CIs) are presented for 2006–2010. Estimated percentages with standard errors for more limited demographic groups are presented for both 2001–2004 and 2006–2010 for a historical comparison. Race/ethnicity is categorized on the basis of the respondents' self-reported race and ethnicity. Non-Hispanic race groups include white, black, American Indian/Alaska Native, Asian, and other or multiple races. Persons of Hispanic ethnicity might be of any race or combination of races. Hispanic subgroups include Puerto Rican, Mexican, and other Hispanic. FPL is based on U.S. Census Bureau poverty thresholds. The poverty threshold is based on the size of the family and the ages of family members. Income divided by the poverty threshold is called the "income-to-poverty ratio" (12).

Multiple years of survey data were combined to provide stable estimates for relatively small respondent groups. If the relative standard error was >30%, or if the sample size (denominator) was <50, estimates were considered unreliable and were suppressed. Analysis software was used to account for the complex survey design, and sample weights were used to produce national estimates. A multivariate (binary response) logistic regression model was used to determine the association (adjusted prevalence ratio [APR]) between reporting an asthma attack in the past year and demographic variables including age, sex, race/ethnicity, educational attainment, FPL, place of birth, and geographic region. A univariate logistic regression model was used to determine the association (crude prevalence ratio) between an asthma attack and each variable separately. The Wald chi-square test statistic was used for all logistic regression models to test for an association between the dependent variable (asthma attack status) and independent variables of interest. Chi-square tests and z-tests were used to test for demographic group and time period differences. All statistical tests were 2-sided, with p<0.05 denoting statistical significance. Comparative terms used to describe findings in this report (e.g., "higher" and "similar") indicate the results of statistical testing at p<0.05.

Results

During 2006–2010, reported attacks among those with current asthma were higher for females (53.5%) than for males (48.8%) (Table 1). The difference in reporting an asthma attack by sex was not statistically significant among children (adjusted prevalence ratio [APR]: 1.1) but was significant among adults (APR: 1.4) after adjusting for age, race/ethnicity, educational attainment, federal poverty level, place of birth, and geographic region (Table 2). Overall, asthma attacks were reported more frequently for children (56.1%) than for adults (49.6%) (Table 1). Asthma attacks were reported more frequently for children aged 0–4 years (APR: 1.9) and 5–11 years (APR: 1.3) than for children aged 12–17 years (Table 2). Among adults, persons aged 18–34 (APR: 1.4), 35–44 (APR: 2.0), 45–54 (APR: 1.9), and 55–64 years (APR: 1.6) were more likely to report asthma attacks than persons aged ≥65 years. Regardless of age, persons with asthma living in the West (54.5%) and the South (53.1%) were more likely to report asthma attacks than persons living in the Midwest (49.4%) and the Northeast (47.8%) (Table 1). The differences in reporting an asthma attack between the South and West regions compared with the reference region (Northeast) remained statistically significant after adjusting for covariates (Table 2). No significant interaction terms or multicollinearity effects were identified among any of the variables in the final model.

For children, reporting an asthma attack did not differ significantly by poverty level (range: 56.3% [FPL <100%]–57.8% [FPL ≥450%]) (Table 1). However, for adults, reporting an asthma attack did differ significantly by poverty level. Adults with incomes <100% of FPL (53.9%; APR: 1.4) and adults with incomes of 100%–249% of FPL (50.1%; APR: 1.2) were more likely to report asthma attacks than adults with incomes ≥450% of FPL (48.9%) (Tables 1 and 2). Among persons with incomes <100% of FPL, asthma attacks did not differ significantly by race/ethnicity, sex, age, level of education, place of birth, or geographic region (Table 1). However, subgroup differences in reported asthma attacks were observed among persons with higher income levels (100%–249% of FPL, 250%–449% of FPL, and ≥450% of FPL). In the three higher income groups, asthma attacks were reported more frequently among females, children, and persons living in the West than among males, adults, and persons living in the Northeast, respectively (Table 1). Notable changes in reporting an asthma attack in the past year were observed between 2001–2004 and 2006–2010 (Table 3). For many demographic groups (whites, blacks, Puerto Ricans, males, females, children, adults, male children, persons with incomes <450% of FPL, and those living in the Northeast and Midwest), reporting an asthma attack decreased significantly. Between 2001–2004 and 2006–2010, the disparity between the various Hispanic subgroups and that between male children and female children were eliminated, and the disparity between adults and children and that among the FPL groups decreased. However, more women than men now report having had an asthma attack in the past year, and persons in the West and the South now report having had an attack more often than persons in the Midwest and the Northeast.

Discussion

Findings from this report are comparable to those of previous reports (1,3,4,6). Within the U.S. population, the percentage of persons with current asthma reporting an asthma attack in the past year varies by demographic and economic groups. Similar to current asthma prevalence, asthma attacks were more prevalent among females, children, the poor, persons of multiple races, and Puerto Ricans. However, while current asthma prevalence was higher in the Northeast, attacks were reported more frequently in the South and in the West than in other regions.

Demographic and socioeconomic characteristics associated with more frequent reporting of asthma attacks (e.g., females, children, persons living in the South and the West, Puerto Ricans, and the poor) were identified. However, causality cannot be determined from cross-sectional survey data. Surveillance data on asthma attacks cannot be used to determine the reasons for the observed differences among the demographic and economic subgroups examined in this report. The differences might be attributable to differing levels of exposure to environmental irritants and allergens (e.g., environmental irritants such as tobacco smoke or air pollutants and environmental allergens such as house dust mites, cockroach particles, and cat and dog dander) (7,9,13) or they might be attributable to differences in disease self-management or medical treatment. The reasons for the differences in the frequency of reported asthma attacks can be addressed only by research studies designed to determine the effect of a specific exposure or a specific disease management protocol.

Limitations

The results of this analysis are subject to at least three limitations. First, the asthma attack prevalence estimates in this report rely on self-reported data and thus are subject to recall bias. The respondent must recall a physician's diagnosis of asthma correctly, which in turn requires that the physician's diagnosis was correct and conveyed successfully to the person. Because no definitive test exists for asthma, the diagnosis and self-report cannot be validated; however, a 1993 review of asthma questionnaires documented a mean sensitivity of 68% and a mean specificity of 94% when self-reported data on an asthma diagnosis were compared with a clinical diagnosis (1). Second, because NHIS includes only the civilian, noninstitutionalized population of the United States, results might not be representative of other populations. Finally, because NHIS is conducted only in English and Spanish, results might not be representative of households whose residents have other primary languages.

Conclusion

With the exception of a few specific occupational exposures, the exact cause of asthma is unknown. Once diagnosed, asthma requires ongoing comprehensive management on a long-term basis. Appropriate management requires both access to the health system and appropriate use of that system. Financial resources and social support are instrumental in long-term management of all chronic conditions, not just asthma (13–15). Acquiring self-management knowledge and skills and limiting exposure to environmental allergens and irritants are necessary to improve health and quality of life for persons with asthma, and especially for those with uncontrolled asthma (2,13–15).

Although surveillance data can identify disproportionately affected groups, research is needed into the role of self-management factors, environmental exposures, health-care system factors, and financial factors to understand better how their interrelations affect individual asthma management and control. Identifying the population-specific factors that contribute to asthma exacerbations among disproportionately affected demographic and socioeconomic groups can lead to targeted interventions. Strategies for asthma self-management and medical treatment protocols for asthma that are culturally appropriate and take into consideration population-specific characteristics can reduce the occurrence and severity of asthma exacerbations (14). For example, an intervention for children with asthma that included the use of multitrigger, multicomponent environmental factors resulted in improved symptom control and reduced the number of school days missed (16). Similar effective interventions are needed to address other disproportionately affected demographic and economic groups identified in this report.

References

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