CGM initiation within 1 year of diagnosis improves long-term glycaemic control

This retrospective, observational study from a single centre in Colorado, US, has previously shown that initiation of continuous glucose monitoring (CGM) within the first year of type 1 diabetes diagnosis results in improved HbA_1c compared with self-monitoring of blood glucose over 2.5 years of follow-up. The present analysis looked at outcomes in the same cohort after 7 years.

The medical records of 396 people newly diagnosed with type 1 diabetes between 2013 and the end of 2015 (the majority aged <18 years) were reviewed. Of these, 81 initiated CGM within 1 year and 315 did not. At 2.5 years’ follow-up, mean HbA_1c was significantly lower in the CGM group (60 vs 78 mmol/mol [7.7% vs 9.3%]). At 7 years, this benefit had persisted (60 vs 84 mmol/mol [7.7% vs 9.8%]). The majority of participants were lost to follow-up at 7 years, with only seven in the original CGM group and 37 in the no-CGM group; nonetheless, the differences remained highly significant. Results did not differ after adjusting for age, sex, insulin delivery method, race and health insurance status.

A group of people who initiated CGM later than 1 year after diagnosis (n=47) was also evaluated. These individuals had a significant reduction in HbA_1c compared with the no-CGM group at 7 years (69 vs 84 mmol/mol [8.5% vs 9.8%]); however, the mean HbA_1c was still higher than in early initiators.

This study is limited by its single-centre design and the small number of participants at the final follow-up, and its retrospective design means that selection bias on the basis of health insurance coverage, socioeconomic status, diabetes education/knowledge and access to healthcare cannot be excluded. It is also notable that people who used their CGM device for less than 70% of the initial study period were excluded.

Despite these limitations, the authors conclude that use of CGM improves glycaemic control in people with type 1 diabetes, and that early initiation results in greater improvements. Initiating CGM early may set a better glycaemic trajectory, and this is important given the well-known effects of early glycaemic control on long-term diabetes outcomes.

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