1 table omitted
Asthma is a chronic inflammatory disorder of the lungs characterized by episodic and reversible symptoms of airflow obstruction.1 During 1993-1994, an estimated 13.7 million persons in the United States reported having asthma, and from 1980 to 1994 the prevalence of self-reported asthma in the United States increased 75%.2 Despite this increase, surveillance data are limited for asthma at the state and local levels.3 To estimate the 1998 prevalence rate of asthma for each state, CDC analyzed national self-reported asthma prevalence data from 1995. This report summarizes the results of the analyses, which project that approximately 17 million persons in the United States have asthma.
For this analysis, persons were considered to have asthma if they had had asthma diagnosed by a physician at some time in their life and had reported symptoms of asthma during the preceding 12 months. Using methods that have been applied elsewhere to forecast cancer rates,4 state-specific asthma prevalence estimates for 1998 were calculated using a three-step procedure: (1) race-, sex-, and age-specific asthma prevalence rates were calculated for each of the four U.S. census regions using data from the 1995 National Health Interview Survey (NHIS); (2) each state's 1998 demographic composition as estimated by the Bureau of Census was multiplied by the corresponding regional prevalences; and (3) linear extrapolations of region-specific increases in asthma prevalence from 1980 to 1994 were applied to the 3-year period from 1995 to 1998 for each state. Confidence intervals and relative standard errors for all estimates were calculated using regression parameters provided by CDC's National Center for Health Statistics for prevalence of chronic conditions.5
In 1998, asthma affected an estimated 17,299,000 persons in the United States. The state with the largest estimated number of persons with asthma was California (2,268,300), followed by New York (1,236,200) and Texas (1,175,100) (Table 1). State-specific prevalence rates ranged from 5.8% to 7.2%. Differences in asthma prevalence rates between states were not significant. By region, 1-year period prevalence estimates ranged from 6.4% to 6.8% in the Northeast, 5.8% to 6.1% in the South, 6.6% to 6.7% in the Midwest, and 6.0% to 7.2% in the West.* The narrow range of prevalence rates within each of these regions indicates that state-specific differences in demographic composition minimally influenced estimated asthma prevalence.
S Rappaport, MPH, B Boodram, MPH, Epidemiology and Statistics Unit, American Lung Association, New York City. Air Pollution and Respiratory Health Br, Div of Environmental Hazards and Health Effects, National Center for Environmental Health; and an EIS Officer, CDC.
The findings in this report project state-specific prevalence rates of 5.8% to 7.2%. These findings are consistent with those from a study in Oregon, which estimated asthma prevalence at 6%-7%.6 However, surveys of self-reported asthma prevalence in Bogalusa, Louisiana,7 Chicago, Illinois,8 and Bronx, New York9 all indicated estimates considerably higher than those in this report. State program planners can use these findings to estimate the burden of asthma within their states.
The findings in this report are subject to at least two limitations. First, the findings assume a linear growth in asthma prevalence since 1995. Although this linear assumption was selected after review of regional growth trends in asthma prevalence during the preceding 15 years,2 changes in the trends of self-reported asthma rates that may have occurred in the 3-year interval during 1995-1998 could not be captured by these linear extrapolations. Second, these results are based on the assumption that age, sex, and race-specific rates of asthma do not vary within any of the four geographic regions of the United States. Each state's estimated prevalence reflects its regional placement in the United States and its demographic composition. These analyses do not account for differences among states in the relative presence or absence of environmental risk factors in asthma prevalence, possible differences in genetic susceptibility toward the condition, or other sociodemographic indicators (e.g., poverty status). As a result, these findings underestimate the variability in asthma prevalence between states within regions. They also do not accurately represent asthma prevalence in geographic subpopulations within states.
Asthma is the ninth leading cause of hospitalization nationally.10 Its severity can be managed with appropriate medical treatment, education, and environmental modification.1 However, fewer than 10 states have conducted asthma prevalence surveys. The initiation of state-based asthma control and management programs will require better state and local data on asthma prevalence to evaluate the effectiveness of these programs. State-level surveillance could incorporate existing data such as hospital discharge data and managed-care data. Questions about asthma could also be added to state and community-level surveys such as the State and Local Integrated Telephone Survey and other surveys conducted in individual states such as the Behavioral Risk Factor Surveillance System.
State-based surveys should include questions related to asthma diagnosis, severity, management techniques, and known geographic and household risk factors. These surveillance data will provide a foundation for planning and evaluating asthma-control programs, identifying high-risk and hard-to-access populations, and structuring health promotion and education initiatives.
Forecasted State-Specific Estimates of Self-Reported Asthma Prevalence— United States, 1998. JAMA. 1999;281(6):507-508. doi:10.1001/jama.281.6.507-JWR0210-4-1