This study aimed to demonstrate the effectiveness of long-term use of intermittently scanned continuous glucose monitoring (isCGM) in adult patients with type 1 diabetes.

Design and methods

In this retrospective real-world study, 689 patients with type 1 diabetes who were >18 years of age and using isCGM were identified from the electronic patient records in North Karelia, Finland. A1C data were collected before and after the initiation of isCGM. The primary outcome was a change in the mean A1C over time after isCGM started.


The greatest reductions in the mean A1C levels were observed 6 months (−0.54% [−5.9 mmol/mol], P <0.001) and 12 months (−0.42% [−4.6 mmol/mol] P <0.001) after the initiation of isCGM. Reduction in A1C remained significant for 4 years, although the mean reduction in A1C was −0.18% (−2.05 mmol/mol) (P = 0.009) at 48 months compared with baseline. In a subgroup analysis, patients with a baseline A1C >9% (75 mmol/mol) benefited the most from initiation of isCGM (reduction −0.97% [−10.6 mmol/mol], P <0.001 at 12 months and −0.92% [−10.1 mmol/mol], P <0.001 at 48 months). Neither sex nor age at the start of isCGM were correlated with A1C reduction.


Use of isCGM improves A1C levels significantly in adult patients with type 1 diabetes. Significant reduction in A1C persisted over 4 years of use, although the effect diminished over time.

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