The Five‐Year Effect of Medicaid Expansion on Community Health Centers: Coverage, Quality of Care, and Service Volume
Authors: Cole M. 
Published: August 2020

Our objective was to assess the five‐year impact of Medicaid expansion on community health centers using nationally representative data on all US health centers, where 35% of the patient population was uninsured prior to expansion. We examined the impact of expansion on insurance coverage and type, quality of care, and utilization of services. Understanding longer term effects of expansion is critical given that some quality measures may take multiple years to be clinically affected while pent‐up demand may also result in short‐term effects on utilization.Using the 2011‐2018 Uniform Data System, we conducted a difference‐in‐differences (DID) analysis with inverse probability of treatment weights (IPTWs), based on propensity scores, to compare outcomes in centers located in expansion versus nonexpansion states. Outcomes included insurance coverage type (none, Medicaid, private), 47 utilization measures (number of patient visits) for select categories of service and chronic conditions based on CPT and ICD codes, and 8 primary care quality measures that may be sensitive to Medicaid expansion. Propensity scores included 23 baseline covariates (patient demographics, health center organizational features, county‐level characteristics). For each measure, using IPTWs, a difference‐in‐difference was calculated using generalized linear models. We included a treatment indicator, time in postperiod indicator, treatment*post‐time interaction, vector of time‐variant covariates, state and year fixed effects, and clustered errors at the center‐level.100% sample of US health centers (N = 1061 centers/year, or 24.5 million patients/year, after exclusions).By 2018, compared to centers in nonexpansion states, centers in expansion states experienced a 12.0 percentage‐point decrease in the percent patients without health insurance (P < .001) and a 13.2 percentage‐point increase in those with Medicaid coverage (P < .001). These gains were largely driven by coverage gains in 2014‐2015.Medicaid expansion was associated with improved quality of care for 5 of 8 measures, though relative gains in quality dissipated over the five‐year postperiod for some measures (eg, asthma treatment) while relative gains for other measures (eg, colorectal cancer screening, diabetes control) were not detected until several years postexpansion. For instance, by 2018, expansion was a 4.5 percentage‐point relative increase in rates of HbA1c control among diabetics (95% CI 2.2‐6.8) and a 3.5 percentage‐point relative increase in colorectal cancer screening rates (95% CI 0.1‐6.9); neither measure was statistically affected until 3 years postexpansion.By 2018, Medicaid expansion was associated with relative increases in 31 of 47 patient visit measures. Effect sizes in 2018 were greatest for visits for HIV testing (IRR = 2.02), hepatitis C testing (IRR = 1.88), mammograms (IRR = 1.45), alcohol disorder (IRR = 1.50), depression (IRR = 1.47), and other mental health (IRR = 1.77) (P < .01).The first five years of Medicaid expansion were associated with increases in insurance coverage, measured quality, and visit volume among health center patients, where effects on quality of care for measures such as diabetes control were not detected until three years into the postperiod.Findings highlight the longer term, significant role of Medicaid expansion in improving quality and in building capacity for health centers. This is particularly important in light of federal and state decisions about the future of Medicaid and extension of health center grant funding.Agency for Healthcare Research and Quality.