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

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. 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. Retrospective analysis of a randomized clinical trial. 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. 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. 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. 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.