Basal Insulin Initiation in Adults With Type 2 Diabetes Mellitus: A Retrospective Cohort Study Using Administrative Health Data in Alberta, Canada

Objectives: Pharmacologic treatment of type 2 diabetes mellitus (T2DM) follows a stepwise approach. Typically, metformin monotherapy is first-line treatment, followed by other noninsulin antihyperglycemic agents (NIAHAs) or progression to insulin if glycated hemoglobin (A1C) targets are not achieved. We aimed to describe real-world patterns of basal insulin initiation in people with T2DM and A1C not at target despite treatment with at least 2 NIAHAs.

Methods: A retrospective cohort study was conducted using administrative health data from Alberta, Canada, among adults with T2DM, indexed on the first test with 7.0% < A1C < 9.5% (April 1, 2011, to March 31, 2019), with at least 2 previous NIAHAs but no insulin. Kaplan-Meier (KM) methodology was used to analyze time to basal insulin initiation, with stratification by index A1C. Annual patient status was categorized into 5 groups: basal insulin initiation, death, NIAHA intensification, no change in therapy (subgroups of A1C <7.1% and A1C ≥7.1% [clinical inertia]), or discontinuance.

Results: The cohort included 14,083 individuals. The KM cumulative probability of initiating basal insulin was 7.7% (95% confidence interval [CI] 7.3% to 8.2%) at 1 year, increasing to 43.1% (95% CI 42.1% to 44.1%) at 8 years of follow-up. Higher A1C levels were associated with greater proportions of basal insulin initiation. By year 8, proportions with NIAHA intensification and clinical inertia were 12.1% and 19.3%, respectively, relative to year 7.

Conclusions: Despite current clinical practice guidelines recommending achieving A1C targets within 6 months, less than half of the individuals with T2DM and clear indications for basal insulin initiated treatment within 8 years. Efforts to reduce delays in basal insulin initiation are needed.