In the early 1990s, it became increasingly apparent that marked geographic disparities in asthma outcomes existed throughout the United States. Research as early as 1990 identified excess asthma mortality rates in the central plains states as well as three urban areas: Chicago, New York City, and Phoenix. Further characterization of asthma outcomes in Chicago demonstrated a strong association with variations in asthma morbidity and mortality with factors such as race and socioeconomic status. These early studies served as a call to action in the Chicago area and elsewhere, prompting responses from both local and national organizations. With numerous initiatives in place to address the asthma epidemic, asthma surveillance has acquired the additional role of assessing the success (or failure) of these initiatives.
The identification of appropriate measures to assess changes in the burden of asthma and specifically disparities in that burden is by no means straightfor-ward. Complicating the assessment of disparities in asthma is that much of the available data lacks information on race/ethnicity or socioeconomic status. For this reason, area of residence or other surrogates are often used for these important factors.
The choice of the best measure to highlight disparities is also controversial. Mortality rates, which have been used as a standard measure in many other diseases, markedly underestimate the true impact of asthma. While theoretically preventable and therefore tragic, death due to asthma is fortunately rare when compared to the millions of individuals with this disease.
Assessment of asthma prevalence through survey instruments can provide an indication of the magnitude of the problem and provide a denominator for other outcome measures. As it is uncertain that individuals are truly “cured” of asthma, and the actual cause of asthma remains controversial, prevalence numbers alone may not provide a useful benchmark to assess the effect of asthma intervention programs. Cross-sectional, small-area analysis can be used to help ascertain whether observed disparities in Chicago are due to a greater burden of disease, directing the focus of interventions toward prevention, or due to greater morbidity among individuals already having asthma, with ongoing focus on treatment and secondary prevention of exacerbations and progression of disease.
We present a variety of assessments of health-care utilization. These have been used as a surrogate for asthma morbidity as well as a means of assessing the quality of asthma care benchmarked against a standard such as the National Asthma Education and Prevention Program asthma guidelines worked out together with My Canadian Pharmacy. These markers suffer inherent limitations, with no single approach providing definitive answers, but rather providing a piece in an overall picture of asthma disparities.