Aim: Sitagliptin can potentially preserve beta cell function by promoting local action of GLP-1 in the pancreas. This study examined if early addition of sitagliptin to metformin is associated with a delay in the progression of type 2 diabetes.

Methods: Administrative health records from Alberta, Canada between April 1, 2008 and March 31, 2015 were used to conduct a retrospective cohort study. New metformin users were identified and included if they added sitagliptin during follow-up. Patients costarting therapy with sitagliptin and metformin were compared to those who added sitagliptin after initial metformin therapy. Potential confounding variables included age, sex, comorbidities, and cardiovascular medications at baseline. A multivariable logistic regression model was used to evaluate the association between sitagliptin addition (costart versus delayed) and insulin initiation. Change in A1c 1 year after adding sitagliptin was evaluated using a multivariable linear regression model.

Results: Mean (SD) age of the 8,746 included patients was 52.1 (11.1) years, 5,655 (64.7%) were men, and 1,149 (13.1%) costarted treatment with metformin and sitagliptin. Insulin was added to the therapy of 192 (16.7%) costarters and 1,640 (21.6%) of delayed sitagliptin users (adjusted odds ratio 0.73; 95% CI: 0.62 to 0.86). The A1c change 1 year after starting sitagliptin was greater in the costarters (-2.1%; SD 2.8%) compared to delayed sitagliptin users (-1.0%; SD 1.9%). After adjusting for baseline A1c and other covariables, costarters had a greater reduction in A1c -0.56% (95% CI: -0.74% to -0.38%).

Conclusions: Costarting sitagliptin with metformin is associated with a lower likelihood of disease progression in newly treated patients with type 2 diabetes compared with adding sitagliptin later in therapy.


S.A. Campbell: None. P.E. Light: None. S.H. Simpson: None.


Canadian Institutes of Health Research

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