Toward Defining the Threshold Between Low and High Glucose Variability in Diabetes

OBJECTIVE To define the threshold for excess glucose variability (GV), one of the main features of dysglycemia in diabetes. RESEARCH DESIGN AND METHODS A total of 376 persons with diabetes investigated at the University Hospital of Montpellier (Montpellier, France) underwent continuous glucose monitoring. Participants with type 2 diabetes were divided into several groups-groups 1, 2a, 2b, and 3 (n = 82, 28, 65, and 79, respectively)-according to treatment: 1) diet and/or insulin sensitizers alone; 2) oral therapy including an insulinotropic agent, dipeptidyl peptidase 4 inhibitors (group 2a) or sulfonylureas (group 2b); or 3) insulin. Group 4 included 122 persons with type 1 diabetes. Percentage coefficient of variation for glucose (% CV = [(SD of glucose)/(mean glucose)] 3 100) and frequencies of hypoglycemia (interstitial glucose < 56 mg/dL [3.1 mmol/L]) were computed. RESULTS Percentages of CV (median [interquartile range]; %) increased significantly (P < 0.0001) from group 1 (18.1 [15.2-23.9]) to group 4 (37.2 [31.0-42.3]). In group 1, the upper limit of % CV, which served as reference for defining excess GV, was 36%. Percentages of patients with % CVs above this threshold in groups 2a, 2b, 3, and 4 were 0, 12.3, 19.0, and 55.7%, respectively. Hypoglycemia was more frequent in group 2b (P < 0.01) and groups 3 and 4 (P < 0.0001) when subjects with a % CV > 36% were compared with those with % CV oe 36%. CONCLUSIONS A% CV of 36% appears to be a suitable threshold to distinguish between stable and unstable glycemia in diabetes because beyond this limit, the frequency of hypoglycemia is significantly increased, especially in insulin-treated subjects.