HbA1c is currently the only metric of glucose control showing an association with chronic complications of type 1 diabetes mellitus (T1D). Time in range (TIR, 70-180 mg/dL) measured by real-time continuous glucose monitoring (CGM) might be a better marker. In this study, the investigators studied the clinical significance of a 10% increase of TIR over two years.

Adult subjects (age ≥ 18 years) with T1D were consecutively recruited in three multicenter studies (RESCUE, FUTURE, ALERTT1 studies) organized between September 2014 and 19 November 2021. For the TIRCO study, only the data from patients recruited at the University Hospital of Antwerp were analyzed. Initially, the data from 498 patients were collected. Pregnant patients and patients with beta-cell transplantation were excluded from the study, resulting in the inclusion of 479 patients. Consecutive patients starting CGM were proposed to participate and were included into the study after signing informed consent.

The study population consisted of 445 patients who used Freestyle libre, 21 patients who used CGM in hybrid closed loop and 13 patients who used Dexcom G4 and G6, resulting in a total of 479 patients.

In this project, the investigators looked into the link between TIR versus HbA1c and the presence of chronic complications in adults with T1D.

The primary endpoint was to evaluate the link between TIR and the presence of chronic microvascular complications as formulated by the following research question: "What is the clinical significance of a 10% increase of TIR over two years?"

The secondary endpoint was to assess the link between TIR and independent risk factors for micro- and macrovascular complications such as sex, age, BMI, lipids, blood pressure, HbA1c, time in range, mean glucose, diabetes duration, method of insulin administration (MDI or CSII), type of sensor and sensor compliance.

Inclusion Criteria:

• Type 1 diabetes mellitus
• Using Real-Time Continuous Glucose Monitoring (rtCGM), Intermittently Scanned CGM (isCGM) or (Hybrid) Closed Loop (HCL) as diabetes treatment
• Willing to sign informed consent

Exclusion Criteria:

• Pregnancy
• Patients that had beta-cell transplantation

Adult subjects (age ≥ 18 years) with T1D were consecutively recruited in three multicenter studies (RESCUE, FUTURE, ALERTT1 studies) organized between September 2014 and 19 November 2021. For the TIRCO study, only the data from patients recruited at the University Hospital of Antwerp were analyzed. Initially, the data from 498 patients were collected. Pregnant patients and patients with beta-cell transplantation were excluded from the study, resulting in the inclusion of 479 patients. Consecutive patients starting CGM were proposed to participate and were included into the study after signing informed consent.

The study population consisted of 445 patients who used Freestyle libre, 21 patients who used Standalone CGM and 13 patients who used Dexcom G4 and G6, resulting in a total of 479 patients.