This innovative and timely study will measure the impact of Affordable Care Act (ACA) Medicaid expansions on diabetes mellitus (DM) prevention, treatment, expenditures and health outcomes. To assess this natural policy experiment, the investigators will use electronic health record data from the ADVANCE clinical data research network (CDRN) of the National Patient-Centered Clinical Research Network (PCORnet).

Diabetes mellitus (DM) is one of the most prevalent chronic diseases, affecting over 29 million people in the United States (US). The number of people with DM is expected to increase by 200% between 2005 and 2050, from 16 to 48 million. Health insurance and continued access to healthcare services are essential for optimal DM care and management; thus, it is hypothesized that Affordable Care Act (ACA) Medicaid expansions could substantially improve access to health insurance and essential healthcare services for patients with DM risk (aged ≥45 + overweight) and patients diagnosed with DM. Studies of single state Medicaid expansions showed increased utilization of healthcare services, access to providers, receipt of preventive care services, and improved health outcomes post-expansion; however, past studies did not have concurrent control states. In 2012, the US Supreme Court ruled that states were not legally required to implement ACA Medicaid expansion, creating a 'natural policy experiment' - a unique national opportunity to test the effect of ACA Medicaid expansion on healthcare access and services for patients at risk for DM or diagnosed with DM ('with DM risk or DM'). By January 1, 2015, 28 states and the District of Columbia had implemented the expansion; Medicaid enrollment increased by an estimated 12.9% in expansion states, compared to 2.6% in non-expansion states. The investigators propose to use this unprecedented natural policy experiment to study the effect of state-level Medicaid expansions on DM prevention, treatment, expenditures, and health outcomes. As many persons affected by both DM and the ACA Medicaid expansions receive primary care in safety net community health centers (CHCs), the proposed analyses will use electronic health record (EHR) data from the national ADVANCE clinical data research network (CDRN) of CHCs (ADVANCE is one of 11 CDRNs in the national PCORnet data network). The ADVANCE CDRN has patient-level data from 470 CHCs in 12 Medicaid expansion states (n=1,242,823 patients) and 248 CHCs in 9 non-expansion states (n=830,399 patients). This nationally unique data resource will let the investigators measure pre-post DM-related utilization and receipt of preventive services in expansion versus non-expansion states, illuminating the impact of ACA Medicaid expansions on DM prevention and treatment Our proposed study, Post ACA Reform: EValuation of community hEalth ceNTer care of Diabetes (PREVENT-D) has the following specific aims:

Aim 1. Compare pre-post insurance status, overall visits, and chronic disease management visits among patients with DM risk or DM, in expansion versus non-expansion states.

Aim 2. Compare pre-post receipt of primary and secondary DM preventive services (e.g., screening for obesity, lipid levels, glycosylated hemoglobin) among patients with DM risk or DM, in expansion versus non-expansion states.

Aim 3. Compare pre-post changes in DM-related biomarkers (e.g., body mass index, blood pressure, lipid levels) in patients with DM risk or DM among newly insured (gained Medicaid in post-period), already insured (had coverage in pre- and post-period), and continuously uninsured (no coverage in pre- and post-period) patients in states that expanded Medicaid.

Aim 4: Measure pre-post changes in Oregon Medicaid expenditures among newly insured compared to already insured patients with DM risk or DM.

Inclusion Criteria:

• Patients in intervention and control states aged 20-64

Exclusion Criteria:

• Patients at intervention and control clinics outside of the age range 20-64 Pregnant women to eliminate the possibility of having gestational diabetes mellitus diagnoses

Study eligible patients within electronic health record data from the ADVANCE clinical data research network (CDRN) of PCORnet