Impact of Insulin Initiation and Time to Insulin Initiation on within-Person Change of Healthcare Utilization in Medicaid Enrollees with type 2 Diabetes

Background: Insulin use, time to insulin initiation, and subsequent healthcare utilization in low-income adults with type 2 diabetes (T2DM) are poorly understood.Methods: Our objectives were to examine whether 1) insulin initiation and 2) every 1-year decrease in the time from first-line glucose-lowering agents (GLAs) to insulin initiation reduced healthcare utilization within 12 months after insulin initiation in Pennsylvania (PA) Medicaid enrollees with T2DM. We included a cohort of 12,648 PA Medicaid enrollees (age 47.3±10.3 years) with first-line non-insulin GLAs between 2008 and 2016. Insulin users (N=3,625) were matched with non-insulin users (N=9,023) on dates of 1st GLA prescription and propensity scores calculated based on baseline characteristics to account for potential confounders. Generalized estimating equations models estimated within-person changes in inpatient stays and emergency room (ER) visits 12 months after vs. 12 months before insulin initiation. We performed sensitivity analyses in young (18-45 years) and middle-aged enrollees (>45 to 64 years). Results: The average time from first-line GLAs to insulin initiation was 2.0±1.7 years. Neither insulin initiation (rate ratio [RR]:1.0 [1.0, 1.1]) nor time to insulin initiation (RR: 1.0 [1.0, 1.0]) was associated with within-person change in ER visits. In young T2DM adults, insulin users had a greater subsequent increase in inpatient stays after insulin initiation vs. non-insulin users over the same time period (RR: 1.3 [1.1, 1.5]). Conclusions: In T2DM Medicaid enrollees, no reduction in healthcare utilization was observed after insulin initiation, even in early stages of pharmacotherapy. Studies investigating primary contributors to the increased inpatient use in young insulin users with T2DM are needed.