AIM:To assess the effect of sitagliptin therapy on seasonal fluctuation of glycemic control in Japanese type 2 diabetic patients.METHODS:Participating patients(age:29-80 years) had been treated with conventional oral antidiabetic agents and/or diet and exercise therapy for over 6 mo.From December 2009,35 patients were additionally prescribed oral sitagliptin starting from 50 mg once daily,while 19 patients taking-glucosidase inhibitors were switched to sitagliptin.Twenty-four patients who refused sitagliptin formed the control group.Changes of mean monthly hemoglobin A 1c(HbA 1c) during the “winter holiday season” were compared between groups using Student’s t-test(2008-2009 vs 2009-2010).Statistical significance was accepted at P < 0.05.Multivariate analysis was performed to assess whether sitagliptin use was associated with deterioration or improvement of glycemic control.RESULTS:Both add-on sitagliptin and switching from-glucosidase inhibitors to sitagliptin prevented the seasonal deterioration of glycemic control and tended to improve HbA 1c.Multivariate analysis revealed that both adding and switching to sitagliptin were negatively correlated with deterioration of glycemic control.In 44 patients who continued sitagliptin therapy for another year,elevation of HbA 1c was suppressed without adverse effects.CONCLUSION:Sitagliptin is a suitable oral agent for preventing deterioration of glycemic control during the winter holiday season. AIM: To assess the effect of sitagliptin therapy on seasonal fluctuation of glycemic control in Japanese type 2 diabetic patients. METHODS: Participating patients (age: 29-80 years) had been treated with conventional oral antidiabetic agents and / or diet and exercise therapy for over 6 mo.From December 2009, 35 patients were additionally prescribed oral sitagliptin starting from 50 mg once daily, while 19 patients taking-glucosidase inhibitors were switched to sitagliptin.Twenty-four patients who refused sitagliptin formed the control group. Changes in the number of days hemoglobin A 1c (HbA 1c) during the “winter holiday season” were compared between groups using Student’s t-test (2008-2009 vs 2009-2010) .Statistical significance was accepted at P <0.05. both sitagliptin use was associated with deterioration or improvement of glycemic control .RESULTS: Both add-on sitagliptin and switching from-glucosidase inhibitors to sitagliptin prevented the seasonal deterioration of glycemic control and tended to improve HbA 1c. Multivariate analysis revealed that both adding and switching to sitagliptin were negatively correlated with deterioration of glycemic control. In 44 patients who continued sitagliptin therapy for another year, elevation of HbA 1c was suppressed without adverse effects .CONCLUSION: Sitagliptin is a suitable oral agent for preventing deterioration of glycemic control during the winter holiday season.