Forecasted State-Specific Estimates of Self-Reported Asthma Prevalence -- United States, 1998

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.

Reported by: 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.

Editorial Note

Editorial Note: 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 York (9) 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.

References

1. National Institutes of Health. Practical guide for the diagnosis and management of asthma. Washington, DC: U.S. Department of Health and Human Services, National Institues of Health. (Publication no. 97-4053).

2. CDC. Surveillance for asthma -- United States, 1960-1995. MMWR 1998;47(no. SS-1).

3. Brown CM, Anderson HA, Etzel RA. Asthma: the states' challenge. Public Health Reps 1997;112:198-205.

4. Landis SH, Murray T, Bolden S, Wingo PA. Cancer statistics, 1998. CA Cancer J Clin 1998;48:6-9.

5. CDC. Vital and health statistics: design and estimation for the National Health Interview Survey. Washington, DC: US Department of Health and Human Services, CDC, National Center for Health Statistics, 1989; DHHS publication no. (PHS) 89-1384. (Series 2, no. 110).

6. Ertle AR, London MR. Insights into asthma prevalence in Oregon. J Asthma 1998;35:281-9.

7. Farber HJ, Wattigney W, Berenson G. Trends in asthma prevalence: The Bogalusa Heart Study. Ann Allergy Asthma Immunol 1997;78:265-9.

8. Persky VW, Slezak J, Contreras A, et al. Relationships of race and socioeconomic status with prevalence, severity, and symptoms of asthma in Chicago school children. Ann Allergy Asthma Immunol 1998;81:266-71.

9. Crain EF, Weiss KB, Bijur PE, Hersh M, Westbrook L, Stein RE. An estimate of the prevalence of asthma and wheezing among inner-city children. Pediatrics 1994;94:356-62.

10. CDC. National Hospital Discharge Survey: annual summary, 1995. Washington, DC: US Department of Health and Human Services, CDC; DHHS publication no. (PHS) 98-1794. (Series 13, no. 133).

* Northeast=Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont; Midwest=Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin; South=Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, and West Virginia; West=Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming.

TABLE 1. Forecasted estimates of self-reported asthma prevalence *, by state -- United
States, 1998
=======================================================================================
Region/State                  No. cases    Estimated      (95% CI +)    Standard error
                                           prevalence
---------------------------------------------------------------------------------------
Northeast
  Connecticut                   215,900       6.6%       (5.6%-7.5%)              7.2%
  Maine                          80,300       6.4%       (5.4%-7.4%)              7.8%
  Massachusetts                 401,000       6.5%       (5.6%-7.5%)              7.2%
  New Hampshire                  78,500       6.6%       (5.5%-7.6%)              7.8%
  New Jersey                    540,400       6.7%       (5.7%-7.6%)              7.2%
  New York                    1,236,200       6.8%       (5.8%-7.8%)              7.3%
  Pennsylvania                  800,900       6.6%       (5.6%-7.5%)              7.2%
  Rhode Island                   64,400       6.5%       (5.5%-7.4%)              7.3%
  Vermont                        39,500       6.5%       (5.5%-7.6%)              7.8%
  Total                       3,241,200       6.7%       (5.7%-7.6%)              7.3%

Midwest
  Iowa                          190,100       6.6%       (5.6%-7.6%)              7.5%
  Illinois                      795,200       6.7%       (5.7%-7.6%)              7.5%
  Indiana                       398,400       6.7%       (5.7%-7.7%)              7.3%
  Kansas                        174,900       6.7%       (5.7%-7.6%)              7.3%
  Michigan                      642,300       6.7%       (5.7%-7.7%)              7.5%
  Minnesota                     318,600       6.7%       (5.8%-7.7%)              7.1%
  Missouri                      362,300       6.1%       (4.7%-7.4%)             11.3%
  Nebraska                      112,100       6.7%       (5.7%-7.7%)              7.4%
  North Dakota                   43,600       6.7%       (5.7%-7.6%)              7.3%
  Ohio                          748,200       6.7%       (5.7%-7.6%)              7.4%
  South Dakota                   51,000       6.7%       (5.8%-7.7%)              7.3%
  Wisconsin                     350,800       6.7%       (5.7%-7.7%)              7.2%
  Total                       4,187,600       6.6%       (5.6%-7.6%)              7.4%

South
  Alabama                       280,500       6.0%       (4.8%-7.1%)              9.5%
  Arkansas                      162,600       5.9%       (4.9%-6.9%)              6.9%
  District of Columbia           31,400       5.9%       (3.6%-8.2%)             19.7%
  Delaware                       44,300       5.9%       (4.9%-6.9%)              8.5%
  Florida                       863,900       5.8%       (4.9%-6.8%)              8.0%
  Georgia                       458,700       6.0%       (4.9%-7.2%)              9.7%
  Kentucky                      232,800       5.9%       (4.9%-6.9%)              8.2%
  Louisiana                     265,500       6.1%       (4.8%-7.3%)             10.5%
  Maryland                      307,300       6.5%       (5.6%-7.5%)              7.2%
  Mississippi                   167,900       6.1%       (4.7%-7.4%)             11.3%
  North Carolina                447,200       5.9%       (4.9%-7.0%)              8.9%
  Oklahoma                      191,700       5.8%       (4.8%-6.7%)              7.9%
  South Carolina                228,600       6.0%       (4.8%-7.2%)             10.1%
  Tennessee                     328,300       5.9%       (4.9%-6.9%)              8.3%
  Texas                       1,175,100       6.0%       (5.0%-7.0%)              8.2%
  Virginia                      403,400       5.9%       (4.9%-6.9%)              8.6%
  West Virginia                 108,600       5.8%       (4.9%-6.8%)              8.2%
  Total                       5,697,800       5.9%       (4.9%-7.0%)              8.8%

West
  Alaska                         42,500       6.7%       (5.7%-7.7%)              7.7%
  Arizona                       316,200       6.9%       (6.0%-7.9%)              6.9%
  California                  2,268,300       7.1%       (6.1%-8.0%)              6.8%
  Colorado                      283,700       7.1%       (6.1%-8.0%)              6.8%
  Hawaii                         73,100       6.0%       (4.1%-7.8%)             15.3%
  Idaho                          86,100       6.7%       (5.7%-7.8%)              7.6%
  Montana                        61,600       6.6%       (5.7%-7.6%)              7.4%
  Nevada                        125,700       7.2%       (6.3%-8.1%)              6.4%
  New Mexico                    121,800       6.8%       (5.8%-7.8%)              7.2%
  Oregon                        225,900       6.9%       (5.9%-7.8%)              6.9%
  Utah                          141,200       6.7%       (5.6%-7.8%)              8.1%
  Washington                    391,900       6.9%       (5.9%-7.8%)              6.8%
  Total                       4,172,400       7.0%       (6.0%-8.0%)              7.0%

Total                        17,299,000       6.4%       (5.5%-7.5%)              7.8%
---------------------------------------------------------------------------------------
* 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.
+ Confidence interval.
=========================================================================================

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