Insulin Pump-Long-Term Effects on Glycemic Control: An Observational Study at 10 Diabetes Clinics in Sweden

Aim: This study examined long-term effects of continuous subcutaneous insulin infusion (CSII) in clinical practice on glycemic control in patients with type 1 diabetes. Subjects and Methods: We evaluated all type 1 diabetes patients at 10 diabetes outpatient clinics in Sweden who had been treated with CSII for at least 5.5 years and had valid glycated hemoglobin (HbA1c) data before starting pump use and at 5 years +/- 6 months. Controls treated with multiple daily insulin injections (MDI) over a time-matched period were also evaluated. Results: There were 331 patients treated with CSII at least 5.5 years at the 10 clinics. Of these, 272 (82%) fulfilled the inclusion criteria. Patients treated with CSII were younger than those treated with MDI (mean age, 38.6 vs. 45.6 years; P < 0.001), more were women (56% vs. 43%; P < 0.001), and diabetes duration was shorter (mean, 15.1 years vs. 20.1 years; P < 0.001). After adjusting for variables differing at baseline and influencing the change in HbA1c over the study period, the reduction in HbA1c remained statistically significant at 5 years and was estimated to be 0.20% (95% confidence interval [CI] 0.07-0.32) (2.17 mmol/mol [95% CI 0.81-3.53]) (P = 0.002). The corresponding adjusted reduction at years 1 and 2 was 0.42% (95% CI 0.31-0.53) (4.59 mmol/mol [95% CI 3.41-5.77]) (P < 0.001) and 0.43% (95% CI 0.31-0.55) (4.71 mmol/mol [95% CI 3.38-6.04]) (P < 0.001), respectively. The effect of insulin pump use versus controls on HbA1c decreased significantly with time (P < 0.001). Conclusions: Use of CSII in clinical practice in Sweden is associated with an approximately 0.2% (2 mmol/mol) reduction in HbA1c after 5 years.