Characterizing Severe and Level 2 Hypoglycemia and Associated Risk Factors in Adults with Type 1 Diabetes Using Hybrid Closed-Loop Insulin Pumps

<b><i>Background:</i></b> Despite advances in diabetes technologies, severe hypoglycemia (SH) and level 2 hypoglycemia (Lv2Hypo) persist among hybrid closed-loop (HCL) insulin pump users. This study assessed the relationship of impaired awareness of hypoglycemia (IAH) and other patient characteristics with SH and Lv2Hypo in HCL insulin pump users with type 1 diabetes. <b><i>Methods:</i></b> A cross-sectional survey assessed 6-month SH history, hemoglobin A1C, IAH (using the Hypoglycemia Awareness Questionnaire), and 30-day continuous glucose monitoring (CGM) data among adult HCL insulin pump users recruited from a national U.S. type 1 diabetes patient registry. Analyses included logistic regression, <i>t</i>-tests, and Chi-square tests. <b><i>Results:</i></b> Of 601 participants (female: 54%; mean age: 43), IAH and higher glucose coefficients of variation (CVs) were associated with both SH and spending ≥1% of time in Lv2Hypo (<i>P</i>s < 0.05). Individuals with SH were further characterized as having spent more time with glucose levels >180 mg/dL and >250 mg/dL and having a lower education level (<i>P</i>s < 0.05). CGM hypoglycemia measures were not associated with SH. Age and diabetes duration were not associated with experiencing SH or spending ≥1% of time in Lv2Hypo. Participants who both experienced SH and spent ≥1% of time in Lv2Hypo showed trends toward exhibiting the most severe IAH and the highest glucose CVs. <b><i>Conclusions:</i></b> Among adults with type 1 diabetes using HCL insulin pumps, IAH and higher glucose CVs are risk factors of experiencing SH and Lv2Hypo. Hyperglycemia and lower education level are also associated with a higher risk for experiencing SH.