ABSTRACT/PROJECT SUMMARY LIFESPAN-D (LongItudinal Food security Experiments via SuPplemental Assistance with Nutrition for Diabetes), is the first evaluation of large-scale natural experiments to determine the health and cost-related effects of nutrition assistance (SNAP and WIC) on T2D outcomes across the lifespan. Food insecurity (FI) is a common, potent factor in the development of type 2 diabetes mellitus (T2D) among low-income populations in the US, and a contributor to socioeconomic, racial and ethnic disparities. FI pressures people to consume low-cost carbohydrate- and energy-rich foods that increase the risk of T2D and makes its clinical management more challenging; creates chronic stress; presents a “competing demand” that crowds out attempts to engage in other health-promoting behaviors; and forces individuals with T2D to make difficult choices between paying share of costs for medicine, monitoring or healthcare vs. paying for nutritious food or other essential needs—creating a Sophie's Choice that can worsen T2D controls and accelerate complications. FI populations are also predisposed to trans-generational elevated risk for T2D, in part, through in utero metabolic programming. FI has been associated with increased progression from prediabetes to T2D, increased gestational diabetes (GDM), and increased hospitalizations for glycemic events among low-income populations with T2D. FI can be reduced and dietary quality improved through nutrition assistance programs, yet whether such programs can improve T2D-related outcomes among vulnerable populations remains an unanswered question. We address this critical question across the lifespan, studying two natural experiments in nutrition assistance policy to address the question: To what extent, and among which populations, does reducing FI through nutrition assistance affect T2D and gestational diabetes (GDM) rates, T2D control, and T2D complication-related ED visits and hospitalizations? And what are the health economic implications? First, we will evaluate a new California statewide policy that allows individuals who receive SSI - a federal income supplement program to help aged, blind and disabled people of low income – to now be concurrently eligible for the federal Supplemental Nutrition Assistance Program (SNAP). Using a quasi-experimental design and statewide longitudinal datasets, we will measure cardiometabolic control, ED visits and hospitalizations for complications among low-income individuals with T2D, as well as incident T2D among individuals with prediabetes. Second, we will evaluate a new California policy within the federal Nutrition Program for Women, Infants, and Children (WIC) that is shifting WIC from a paper voucher to an Electronic Benefits Transfer (EBT) card system that will increase uptake of WIC benefits. Using a quasi-experimental design and statewide and national datasets, we will measure effects of eWIC on perinatal outcomes, including GDM and gestational weight g...