The Effects of Medicaid on Access and Adherence to Recommended Preventive Services

Increasing access to health care and utilization of preventive services are important policy goals. Using recent changes in the Medicaid program and instrument variable methods, this paper quantifies the effects of Medicaid enrollment on adult beneficiaries’ access to care and adherence to recommended preventive services. We use nationally representative sample from the Medical Expenditure Panel Survey for 2005-2015, which spans the business cycle. While there is a large literature on the effects of Medicaid enrollment on access and preventive services, our paper contributes to the literature in two distinctive ways. First, we study receipt of services recommended by the United States Preventive Task Forces (USPSTF) within the time frames recommended by the Task Force for the appropriate populations. While most studies examined preventive services use in the past year, the recommended intervals by the USPSTF for preventive services vary widely. To our knowledge, no study has yet examined the causal effects of Medicaid enrollment on adherence in recommended time frames. Second, no other study has used nationally representative data to study the causal effects of Medicaid enrollment on adult preventive services.

Our sample was restricted to low-income, non-elderly adult citizens. We employ a two-stage least squares model to estimate the effects of Medicaid enrollment. We instrument for enrollment with Medicaid eligibility rates derived from a detailed simulation model. To create our instrument for enrollment, we estimate eligibility rates that hold the population constant in the same manner as Currie and Gruber (1996). That is, we apply the rules of each state-year to the entire sample and create separate estimates by state, year, parental status, sex, race/ethnicity, and age, education or income bands. The population-constant eligibility rate was highly predictive of enrollment.

Medicaid enrollment increased access to care significantly. In particular, Medicaid enrollment increased the probability of having a usual source of care by 15.9 percentage points, decreased the probability of having unmet needs for medical care by 9.2 percentage points, and decreased the probability of having delays in medical care by 6.4 percentage points. Medicaid also improved adherence to some recommended preventive services for enrollees. Medicaid increased the probability of having a blood pressure screening in the past year by 11.6 percentage points, and the probability of having a Pap smear in the past 3 years by 12.2 percentage points. We also found that using the recommended time frames for preventive services (instead of a 12 month period time frame for all preventive services) leads to different effects of Medicaid enrollment on adherence. We found a statistically significant effect of Medicaid on cholesterol screening in the past year but not on screening in the past 5 years. On the other hand, the effect of Medicaid on Pap smear in past year is not statistically significant. Churning in Medicaid, public programs for cancer screenings, as well as gender and subpopulation specific factors may explain these differences.