Project Summary As of 2017, over 30 million people in the United States live with diabetes mellitus (DM). DM has many acute and chronic complications (e.g., cellulitis, urinary tract infection, angina and ischemic heart disease, etc.). Patients with DM need access to healthcare (e.g., prescription medications, diabetic eye exams, laboratory monitoring) to control, manage DM, and prevent DM-related complications, a challenging task for patients without continuous health insurance. The Patient Protection and Affordable Care Act (ACA) substantially increased health insurance rates through Medicaid eligibility expansions (in states that chose to expand) and nationwide individual health insurance marketplaces. We studied the impact of the early uptake of Medicaid expansion (2014) on access to and delivery of healthcare among patients with DM in low-income populations and found a greater uptake of health insurance in states that expanded Medicaid relative to those that did not, as well as increased access to preventive care and improved DM control. With increased access to needed care, it is hypothesized that ACA Medicaid expansions will reduce the incidence of DM-related complications; however, this hypothesis has not yet been formally tested. Further, beyond insurance coverage, there are a number of other individual- and community-level social determinants of health (SDH) that likely impact DM- related health outcomes. To our knowledge, no study has investigated how neighborhood or individual characteristics influence the effects of the ACA on DM-related complications. We will leverage electronic health record data from the national ADVANCE clinical research network of community health centers (CHCs) which has patient-level data from 801 CHCs in 22 Medicaid expansion states (n=177,125 adult patients with DM) and 460 CHCs in 7 non-expansion states (n=104,849 adult patients with DM). We will also link these EHR data with mortality and community-level SDH data. The aims of this project are to: 1) evaluate the long-term impact of ACA Medicaid expansions on DM-related complications. 2) compare DM-related complications for those with stable health insurance versus those with unstable coverage; and, 3) understand the moderating effect of individual- and community-level SDH on the relationship between ACA Medicaid expansions and DM-related complications. Our findings will be critical to informing current decisions being made regarding the future of the ACA and additional healthcare reforms being brought forth that could impact millions of patients living with DM.