Predictors of Insulin Initiation in Patients with Type 2 Diabetes: An Analysis of the Look AHEAD Randomized Trial

Background: The decision to initiate insulin in patients with type 2 diabetes is a challenging escalation of care that requires an individualized approach. However, the sociodemographic and clinical factors affecting insulin initiation are not well understood. Objective: We sought to identify patient factors that were independent predictors of insulin initiation among participants in the Look AHEAD (Action for Health in Diabetes) clinical trial. Design: Retrospective analysis of a randomized clinical trial. Participants: Beginning in 2001, Look AHEAD enrolled ambulatory U.S. adults with type 2 diabetes who were overweight or obese and had a primary healthcare provider. Participants were randomized (1:1) to an intensive lifestyle intervention, or diabetes support and education. This study examined 3913 participants across the two trial arms who were not using insulin at baseline. Main Measures: We used Cox proportional hazards models to estimate the association between participant characteristics and time to insulin initiation. We performed time-varying adjustment for HbA1c measured eight times over the 10-year study period, as well as for multiple clinical and socioeconomic factors. Key Results: A total of 1087 participants (27.8%) initiated insulin during a median follow-up of 8.0 years. Age was inversely associated with insulin initiation (adjusted hazard ratio [aHR] 0.88 per 10 years, P = 0.025). The risk of insulin initiation was greater with a higher number of diabetes complications (P < 0.001 for trend); chronic kidney disease and cardiovascular disease were independently associated with insulin initiation. There was a lower risk of insulin initiation in black (aHR 0.77, P = 0.008) and Hispanic participants (aHR 0.66, P < 0.001) relative to white participants. Socioeconomic factors were not associated with insulin initiation. Conclusions: Patient age, race/ethnicity, and diabetes complications may influence insulin initiation in type 2 diabetes, independent of glycemic control. Future work is needed to understand the drivers of racial differences in antihyperglycemic treatment, and to identify patients who benefit most from insulin.