Epidemiologic data regarding the burden of asthma are inconsistent, though as many as a quarter to half of patients with severe uncontrolled asthma (SUA)—which is caused by exacerbations of the disease—require hospitalizations, ED visits, and/or systemic corticosteroids (SCS). Additionally, asthma control and mortality may differ across cities and states, in part because of differences in healthcare delivery and elements patients are exposed to, according to Eugene R. Bleecker, MD.

“You can look at the state of New York as an example,” says Dr. Bleecker. “New York includes a big city, as well as very rural areas, with different healthcare delivery systems and very different exposures.”

For a paper published in Annals of Allergy, Asthma & Immunology, Dr. Bleecker and colleagues aimed to examine the heterogeneity of asthma severity and control in the United States. They reviewed asthma prevalence and morbidity using a US database of 1.5 billion medical and pharmacy claims filed between July 2015 and June 2018. Heatmaps were used to categorize the prevalence of severe uncontrolled asthma in all states and the District of Columbia, as well as 2,935 counties. Investigators also categorized mortality in states (2016) and 3,147 counties (1999-2018) and compared this information with claims-based morbidity.

County-Level Morbidity & Mortality

The analysis included 4,506,527 patients with asthma, 640,936 (14.2%) of whom were treated with age-specific therapy for severe disease. Children aged 0-5 and 6-11, as well as adolescents and adults aged 12 and older comprised 12.1%, 17.7%, and 69.8% of the study population, respectively, according to the study results. More than half of the study population, or 56.2%, was female.

Among those with severe asthma, nearly a quarter—144,232 patients, or 22.5%—filled two or more annual courses of systemic steroids and were classified as having severe uncontrolled asthma.

Most states with increased mortality had comparatively fewer patients with SUA. The researchers observed a significant correlation between mortality and morbidity and trends according to urban/rural and metropolitan status on the county level, according to the study results. Specifically, the average age-adjusted mortality rate in urban counties was 0.31 per 100,000 versus essentially 0.00 in rural counties (P<0.001) and 0.33 in metropolitan/near-metropolitan versus 0.06 in non-metropolitan counties (P<0.001).

“We looked at this across the country,” explains Dr. Bleecker. “The first thing we saw was that there is not a good relationship between morbidity and mortality at the state level. By county, there was a much better relationship between mortality and morbidity rates in severe asthma.”

Regarding medication adherence, among patients on age-specific controller therapy for severe asthma, two-thirds of patients (67.0%) demonstrated less than 50% adherence based on the proportion of days covered, with 45% adhering less than 25% of the time. Only 17.7% of patients had 80% or greater adherence (Figure).

“By looking at the county level, we were able to provide a better view of the true incidence and prevalence of asthma,” Dr. Bleecker notes.

Increasing Awareness

Greater awareness on a local level about the use of SCS may be used in the future as a sign of uncontrolled asthma, according to the study results, and should prompt educational and public health strategies to enhance outcomes.

“For example, say you live in a county that has a high prevalence of SUA,” Dr. Bleecker says. “What do we need to do about it? Intrinsically, asthma is probably managed a good deal through primary care. We need to educate providers about how to manage asthma and when it’s appropriate to seek help or refer patients to a specialist.”