Predictors and consequences of declining insulin therapy by individuals with type 2 diabetes

To determine the relationship between decline of insulin therapy by individuals with type 2 diabetes and subsequent blood glucose control.

We retrospectively studied adults with type 2 diabetes and suboptimal (HbA_1c ≥ 53 mmol/mol [7.0%]) glycaemic control followed at two academic hospitals between 2000 and 2014 who were recommended insulin therapy. Decline of insulin therapy recommendations was identified using natural language processing of provider notes. Time to HbA_1c < 53 mmol/mol (7.0%) served as the primary outcome.

Of 5307 study participants, 2267 (42.7%) declined insulin therapy. Median time to HbA_1c control in individuals who declined vs. started insulin therapy was 50 vs. 38 months, respectively (P < 0.001). In multivariable analysis, decline of insulin therapy was associated with hazard ratio for HbA_1c control of 0.89 (95% CI 0.82 to 0.97; P = 0.008). Participants were more likely to accept insulin therapy recommendations if they had diabetes complications (OR 1.32; 95% CI 1.13 to 1.53; P < 0.001) or a higher HbA_1c (OR 1.10; 95% CI 1.07 to 1.13; P < 0.001), and less likely if they were older (OR 0.81; 95% CI 0.76 to 0.86; P < 0.001) or were taking more non-insulin diabetes medications (OR 0.78; 95% CI 0.74 to 0.83; P < 0.001).

Individuals with uncontrolled type 2 diabetes who declined insulin therapy subsequently had worse glycaemic control. These findings highlight the need to improve our understanding of the relationship of this common but poorly explored clinical phenomenon to blood glucose control and ultimately diabetes complications.