OBJECTIVES: The purpose of this analysis is to estimate the impact of Medicaid Expansion in 2014 on prescription, healthcare services, and various health outcomes among individuals with asthma.

METHODS: A retrospective cross-section study was conducted among asthma patients aged 18-64 years in the United States using the 2006-2016 Medical Expenditure Panel Surveys. The total expenditure and utilization of prescription drug, healthcare services (expenditures and utilization of emergency room (ER), outpatient visit, and hospitalization), and changes of health outcomes (asthma attack rate, probability of quick-relief inhalers utilization, and preventive prescription utilization rate) served as the outcome variables. The outcome variables were estimated by multiple generalized linear models, negative binomial models, and Probit models. To compare changes before and after the expansion for Medicaid beneficiaries and non-beneficiaries, a difference-in-difference structure was used in the model. A two-part model was used to adjust the multiple zero within the variables of utilization and expenditure.

RESULTS: The study included 12,022 asthma patients, and the coverage of Medicaid increased from 30% to 38% after the expansion. Medicaid beneficiaries have higher prescription drug expenditures (p=0.05) and lower utilization (p=0.84) than their counterparts after the expansion. For preventive drugs, such as leukotriene modifiers, out-of-pocket expenditure decreased after the expansion by $11.9 (p=0.07). The probability of taking daily preventive drugs increased by 12.4% (p<.001) after expansion. Probability of asthma attacks and using inhalers increased. After the expansion, ER visits increase by 0.06 times (p<.001).

CONCLUSIONS: Medicaid Expansion was beneficial to asthma patients. But additional studies need to be conducted to identify the reason for increasing asthma-related ER visits when preventive drug utilization also increased.