Heterogeneity of Responses to Real-Time Continuous Glucose Monitoring (RT-CGM) in Patients With Type 2 Diabetes and Its Implications for Application

OBJECTIVE

To characterize glucose response patterns of people who wore a real-time continuous glucose monitor (RT-CGM) as an intervention to improve glycemic control. Participants had type 2 diabetes, were not taking prandial insulin, and interpreted the RT-CGM data independently.

RESEARCH DESIGN AND METHODS

Data were from the first 12 weeks of a 52-week, prospective, randomized trial comparing RT-CGM (n = 50) with self-monitoring of blood glucose (n = 50). RT-CGM was used in 8 of the first 12 weeks. A1C was collected at baseline and quarterly. This analysis included 45 participants who wore the RT-CGM ≥4 weeks. Analyses examined the RT-CGM data for common response patterns—a novel approach in this area of research. It then used multilevel models for longitudinal data, regression, and nonparametric methods to compare the patterns of A1C, mean glucose, glycemic variability, and views per day of the RT-CGM device.

RESULTS

There were five patterns. For four patterns, mean glucose was lower than expected as of the first RT-CGM cycle of use given participants’ baseline A1C. We named them favorable response but with high and variable glucose (n = 7); tight control (n = 14); worsening glycemia (n = 6); and incremental improvement (n = 11). The fifth was no response (n = 7). A1C, mean glucose, glycemic variability, and views per day differed across patterns at baseline and longitudinally.

CONCLUSIONS

The patterns identified suggest that targeting people with higher starting A1Cs, using it short-term (e.g., 2 weeks), and monitoring for worsening glycemia that might be the result of burnout may be the best approach to using RT-CGM in people with type 2 diabetes not taking prandial insulin.In a 12-month, prospective, randomized controlled trial of real-time continuous glucose monitoring (RT-CGM) in people with type 2 diabetes and not taking prandial insulin, we demonstrated that intermittent RT-CGM used for a period of 12 weeks was associated with a clinically significant reduction in A1C during the same period of time compared with premeal and bedtime self-monitoring of blood glucose (SMBG) and that the improvement in A1C was sustained for at least 40 weeks after the active intervention ended (1,2). Previous studies of RT-CGM for people with type 2 diabetes (3–5), although smaller and including mostly patients taking prandial insulin, have observed similar improvements in glycemia.Owing to fluctuations around the mean, people with the same A1C can have different glycemic variability (6,7). Some researchers have proposed that higher glycemic variability may increase the risk for diabetes complications (8–10) through increased oxidative stress (11,12). However, these studies of RT-CGM in people with type 2 diabetes did not address whether glycemic variability was also reduced concomitantly with A1C and did not report whether there were different patterns of responses to using the device and when the responses might have occurred. Were responses immediate or gradual, temporary or sustained, marked or modest? These questions are important because their answers may inform clinicians how RT-CGM might be implemented in practice for people with type 2 diabetes who are not taking prandial insulin.Thus, the present analysis sought to answer those questions through an in-depth investigation of each participant’s raw glucose data from their RT-CGM and identification of common response patterns. This led to a new typology describing glucose responses, which we verified by statistical analyses of measures of mean glucose, glycemic variability, and patient engagement with the RT-CGM device.