, Volume 4, Issue 4, pp 251-256

Determinants of the HbA1c-lowering effect of sitagliptin when added to ongoing insulin therapy in Japanese patients with type 2 diabetes

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Abstract

Aims

This study assessed the independent predictors of the HbA1c-lowering effect of sitagliptin when added to ongoing insulin therapy in Japanese patients with type 2 diabetes.

Methods

Data were retrieved from the medical records of 179 patients with type 2 diabetes on stable-dose insulin alone or stable-dose insulin and oral hypoglycemic agents who received sitagliptin (25 or 50 mg) added on once daily for inadequate glycemic control for at least 12 weeks. Spearman’s rank correlation coefficient analysis was performed to assess the correlations of two independent continuous variables. Multiple stepwise regression analysis was used to search for independent predictors of reduction in HbA1c levels after 12 weeks of sitagliptin add-on treatment (ΔHbA1c).

Results

Among all subjects, ΔHbA1c was significantly correlated with baseline HbA1c alone (r = 0.410, P < 0.0001). However, multiple stepwise regression analysis using baseline variables revealed that the three independent factors contributing to ΔHbA1c were baseline HbA1c (r 2 = 0.16, P < 0.0001), total daily insulin dose (r 2 = 0.05, P = 0.002), and diabetes duration (r 2 = 0.03, P = 0.006).

Conclusions

The results suggest that an increased total daily insulin dose and prolonged diabetes duration contribute in part to the attenuation of the HbA1c-lowering effect of sitagliptin added to ongoing insulin therapy in Japanese patients with type 2 diabetes. A prospective analysis of a larger population with a longer study duration is warranted to confirm these findings.