Relationship of continuous glucose monitoring-related metrics with HbA1c and residual β-cell function in Japanese patients with type 1 diabetes

Abstract

The targets for continuous glucose monitoring (CGM)-derived metrics were recently set; however, studies on CGM data over a long period with stable glycemic control are limited. We analyzed 194,279 CGM values obtained from 19 adult Japanese patients with type 1 diabetes. CGM data obtained during stable glycemic control over four months were analyzed. CGM-related metrics of different durations “within 120, 90, 60, 30, and 7 days” were calculated from baseline. Time in range (TIR; glucose 70–180 mg/dL), time above range (TAR; glucose ≥ 181 mg/dL), and average glucose levels, but not time below range (TBR; glucose ≤ 69 mg/dL), strongly correlated with glycated hemoglobin (HbA1c) values (P < 0.0001). TBR correlated with glucose coefficient of variation (CV) (P < 0.01). Fasting serum C-peptide levels negatively correlated with glucose CV (P < 0.01). HbA1c of approximately 7% corresponded to TIR of 74% and TAR of 20%. The shorter the CGM period, the weaker was the relationship between HbA1c and CGM-related metrics. TIR, TAR, and average glucose levels accurately reflected HbA1c values in Japanese patients with type 1 diabetes with stable glycemic control. Glucose CV and TBR complemented the limitation of HbA1c to detect glucose variability and hypoglycemia. Stable glycemic control with minimal hypoglycemia depended on residual β-cell function.

Capturing the real‐world benefit of residual β‐cell function during clinically important time‐periods in established Type 1 diabetes

“…Through analysis of clinically meaningful time periods during free‐living, we have demonstrated for the first time that increasing β‐cell function in type 1 diabetes is associated with improved glycaemia overnight and postprandially. This builds upon previous work demonstrating that individuals with residual β‐cell function spend less overall free‐living time in hyperglycaemia or hypoglycaemia compared with those with undetectable β‐cell function 5–7 . Specifically, we show that Cpep high spent the most time in normoglycaemia overnight and had the lowest nocturnal variability.…”

“…This builds upon previous work demonstrating that individuals with residual βcell function spend less overall freeliving time in hyperglycaemia or hypoglycaemia compared with those with undetectable βcell function. [5][6][7] Specifically, we show that Cpep high spent the most time in normoglycaemia overnight and had the lowest nocturnal variability. We also demonstrated Cpep und spent less time in normoglycaemia in postprandial periods (0-300 min).…”

“…3,4 Continuous glucose monitoring (CGM) measurements over 1-17 week have found that, increased time in normoglycaemia, reduced time spent in hyperglycaemia, reduced time spent or incidence of hypoglycaemia, and reduced glycaemic variability, all associate with increased βcell function in short-and longer-duration type 1 diabetes. [5][6][7][8] However, it is unknown when these improvements occur during the day.…”

“…Residual β‐cell function in type 1 diabetes is associated with improved free‐living glycaemic control, with increased C‐peptide secretion associated with reduced HbA1c and hypoglycaemic events 3,4 . Continuous glucose monitoring (CGM) measurements over 1–17 week have found that, increased time in normoglycaemia, reduced time spent in hyperglycaemia, reduced time spent or incidence of hypoglycaemia, and reduced glycaemic variability, all associate with increased β‐cell function in short‐ and longer‐duration type 1 diabetes 5–8 . However, it is unknown when these improvements occur during the day.…”

Insulin Requirement and Complications Associated With Serum C-Peptide Decline in Patients With Type 1 Diabetes Mellitus During 15 Years After Diagnosis

“…Moreover, with the wide use of continuous glucose monitoring (CGM) systems, recent studies reported on the importance of glycemic variability and its association with C-peptide levels. Patients with residual C-peptide production had a lower mean blood glucose level and higher time in range ( 30 ), and fasting C-peptide levels were negatively correlated with glucose coefficient of variation by CGM ( 31 ). The present study confirmed the lower insulin requirement and lower incidence of DKA events in patients with residual C-peptide secretion, but no significant association with HbA1c levels and microvascular complications.…”