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

Abstract

Aims/hypothesis: The aim of this work was to evaluate changes in glycaemic control (HbA1c) 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 HbA1c and events of severe hypoglycaemia were compared.

Results: After the start of FM, the difference in IPTW change in HbA1c 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 HbA1c was greatest in those with baseline HbA1c ≥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 HbA1c ≤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 HbA1c, most evident in those with higher baseline HbA1c levels. In addition, FM users experienced lower rates of severe hypoglycaemic events compared with control individuals using SMBG for self-management of glucose control.

Keywords: Continuous glucose monitoring; Flash glucose monitoring; Glucose control; Hypoglycaemia; Type 1 diabetes.

Figures

Fig. 1

Flow chart for selection process of the study population

Fig. 2

Weighted (IPTW) change in HbA1c and 95% CIs for FM users and control individuals during the observational period from index up to 20 months after index. n=the total number of observations contributing at each time point

Fig. 3

General updated mean HbA1c for FM users (a) and for control individuals (b), categorised into low (≤52 mmol/mol), intermediate (53–69 mmol/mol) and high (≥70 mmol/mol) HbA1c levels. The graphs show unadjusted data, therefore a comparison between the groups based on the figure should be made cautiously as data are not adjusted for confounders. The shaded area depicts indicative 95% CIs for the smooth functions of HbA1c. Note that the 95% CI does not account for multiple repeated measures from the same individual. The spikes in the graph depicting general updated mean for HbA1c observed pre-index in the group with HbA1c ≥70 mmol/mol and the pre-index dips in the group with HbA1c ≤52 mmol/mol are caused by the effect of the ‘regression to the mean’ and are accordingly not associated with an effect of an intervention or selection bias