Effect of flash glucose monitoring in adults with type 1 diabetes: a nationwide, longitudinal observational study of 14,372 flash users compared with 7691 glucose sensor naive controls

AIMS/HYPOTHESIS: The aim of this work was to evaluate changes in glycaemic control (HbA(1c)) and rates of severe hypoglycaemia over a 2 year period after initiation of flash glucose monitoring (FM) in type 1 diabetes. METHODS: Using data from the Swedish National Diabetes Registry, 14,372 adults with type 1 diabetes with a new registration of FM during 2016–2017 and with continued FM for two consecutive years thereafter, and 7691 control individuals using conventional self-monitoring of blood glucose (SMBG) during the same observation period, were included in a cohort study. Propensity sores and inverse probability of treatment weighting (IPTW) were used to balance FM users with SMBG users. Changes in HbA(1c) and events of severe hypoglycaemia were compared. RESULTS: After the start of FM, the difference in IPTW change in HbA(1c) was slightly greater in FM users compared with the control group during the follow-up period, with an estimated mean absolute difference of −1.2 mmol/mol (−0.11%) (95% CI −1.64 [−0.15], −0.75 [−0.07]; p < 0.0001) after 15–24 months. The change in HbA(1c) was greatest in those with baseline HbA(1c) ≥70 mmol/mol (8.5%), with the estimated mean absolute difference being −2.5 mmol/mol (−0.23%) (95% CI −3.84 [−0.35], −1.18 [−0.11]; p = 0.0002) 15–24 months post index. The change was also significant in the subgroups with initial HbA(1c) ≤52 mmol/mol (6.9%) and 53–69 mmol/mol (7.0–8.5%). Risk of severe hypoglycaemic episodes was reduced by 21% for FM users compared with control individuals using SMBG (OR 0.79 [95% CI 0.69, 0.91]; p = 0.0014)]. CONCLUSIONS/INTERPRETATION: In this large cohort, the use of FM was associated with a small and sustained improvement in HbA(1c), most evident in those with higher baseline HbA(1c) levels. In addition, FM users experienced lower rates of severe hypoglycaemic events compared with control individuals using SMBG for self-management of glucose control. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains peer-reviewed but unedited supplementary material available at 10.1007/s00125-021-05437-z.