Objectives: Nine classes of glucose-lowering agents (GLAs) are available for patients with type 2 diabetes prior to starting insulin. This study's aim was to determine if the number of GLAs is associated with a difference in glycated hemoglobin (A1C) at insulin initiation in the US Department of Veterans Affairs Health Care System (VAHCS).
Study design: Retrospective cohort study.
Methods: A retrospective cohort with national Veterans Health Administration data was created. Veterans with type 2 diabetes and first insulin prescription filled in the VAHCS between January 1, 2009, and August 28, 2013, were identified. Included veterans refilled insulin within the first year, had an A1C > 7% (53 mmol/mol) at least 60 days prior to insulin initiation, and received a GLA within 6 months prior to insulin. Veterans were grouped into 4 cohorts according to the number of GLAs used.
Results: A total of 90,497 veterans with type 2 diabetes met inclusion criteria. Insulin was initiated at a mean A1C of 9.9% (85 mmol/mol). The mean A1Cs prior to insulin for 1, 2, 3, or > 3 GLAs were 10.3% (89 mmol/mol), 9.9% (85 mmol/mol), 9.6% (81 mmol/mol), and 9.6% (81 mmol/mol), respectively. Months to insulin increased with the number of GLA trials and prolonged the time veterans were exposed to A1C > 8% (64 mmol/mol).
Conclusions: Multiple glucose-lowering drug classes are associated with a numerical, but not a clinical, difference in A1C at insulin initiation in the closed formulary of the VAHCS.