Spatial analysis of disparities in asthma treatment among adult asthmatics

Background: Spatial analytic techniques can uncover important differences in asthma treatment and identify geographic areas with poor asthma management. Objective: To review geographical differences in asthma treatment in an adult asthmatic population. Methods: This was a retrospective, cross-sectional chart review study (n=519) using Geographic Information System approaches to determine the impact of spatial access to pharmacies and other factors on inappropriate rescue and inadequate controller medication use. Statistical analyses included chi-square test for categorical variables and Kruskall-Wallis test for continuous variables. Logistic regression was used to determine unadjusted and adjusted odds of inappropriate and inadequate pharmaceutical management of asthma based upon distance to pharmacy and other factors. Choropleth maps were constructed to display zip code level variation of asthma management. Results: Inappropriate medication users lived further from their preferred pharmacy compared to appropriate users (median distances of 3.02 and 1.96 miles respectively; p=0.01). Inappropriate and inadequate management of asthma varied by zip code, ranging from 5.5 to 17.3% and 25.0-59.6%, respectively. A statistically significant difference in appropriate use by age was found, with nearly 17% of adults age 65 and older overusing their rescue inhaler. Conversely, patients age 18-34 years, 35-49 years, and 50-64 years, used their controller medications inadequately (64.2%, 57.3%, and 48.2%, respectively) compared to 42.5% of patients aged 65 and older. Unadjusted and adjusted analyses showed that former smokers had higher odds of inadequate management of asthma. Conclusion: The unadjusted findings suggest that distance to pharmacies may play a role in the pharmaceutical management of asthma, though these findings are explained by confounding factors. Future research should continue to explore the effect of spatial access to pharmacies on chronic disease management and the role that maps can play in guiding medication management interventions in a larger sample to allow for more rigorous analysis.