Supplementary Material for: Social Determinants of Health Impact on Pediatric Type 1 Diabetes Outcomes Early After Diagnosis

Introduction: Disparities in diabetes technology use and glycemic outcomes among US youth with type 1 diabetes (T1D) are strongly associated with race/ethnicity and insurance. The Social Deprivation Index (SDI) offers a multidimensional measure of area-level socioeconomic disadvantage linked to poorer health outcomes in pediatric populations. Methods: We conducted a retrospective cohort study (1,541 youth < 19 years) newly diagnosed with T1D between 2018–2022 at a single tertiary care center. SDI was calculated from address and categorized into quintiles (Q1 least deprived). Primary outcomes included time to continuous glucose monitor (CGM) and insulin pump initiation, and hemoglobin A1c (A1c) over 12 months. Differences by SDI quintile were assessed using interval-censored Cox proportional hazards and linear mixed-effects models. Results: Within one year, 84% initiated CGM and 50% initiated pump therapy. Time to CGM initiation increased across SDI quintiles; patients in Q3–Q5 were significantly less likely to initiate CGM than Q1 (Q3 HR, 95% CI: 0.81, 0.66-0.99, p = 0.036; Q4 0.81, 0.67-0.98, p = 0.027; Q5 0.69, 0.56-0.86; p = 0.001). Hispanic, non-Hispanic Black, and Medicaid-insured patients had lower CGM uptake. Pump initiation was significantly lower only in Q5. Among CGM users, Q5 had higher A1c than Q1 (difference 0.80%, p = 0.001). Among non-pump users, Q4 and Q5 had higher A1c than Q1. AID users had lower A1c than pump-only users (7.0% vs 7.2%, p = 0.003). Conclusion: A1c is lower across all SDI levels with CGM use, but disparities persist. Addressing structural barriers is essential to achieving equity.