To understand the severity and potential impact of heterogeneity in definitions of hypoglycemia used in diabetes research, we aimed to review the hypoglycemia definitions adopted in randomized controlled trials (RCTs).
We reviewed 109 RCTs included in the Canadian Agency for Drugs and Technologies in Health reports for the second- and third-line therapy for the patients with type 2 diabetes (T2D).
Nearly 60% (n=66) of the studies reviewed presented the definitions for overall hypoglycemia, and another 20% (n=22) of the studies reported the results for hypoglycemia but did not report a definition. Among these 66 studies, only 9 (14%) followed the American Diabetes Association/European Medicines Agency specified guidelines to define hypoglycemia, with an exact threshold of plasma glucose ≤3.9 mmol/L. Fifty-two of the 66 studies (79%) used a threshold considerably lower than the recommended ≤3.9 mmol/L, and 16 studies used a threshold between 3.8 and 4.0 mmol/L. The proportion of the trials that used a cutoff value of <3.1 mmol/L appeared to be slightly similar among the more commonly used non-insulin treatments, GLP-1s (7 of 18 [39%]), thiazolidinediones (TZDs; 6 of 11 [55%]), DPP-4s (12 of 19 [64%]), and sulfonylureas (11 of 20 [55%]). Among trials with intermediate-long-acting insulins (neutral protamine Hagedorn insulin, detemir, glargine), 7 of 26 trials (27%) used a cutoff of <3.1 mmol/L. The definition of severe hypoglycemia was also subject to substantial heterogeneity, in both the utilized threshold and accompanying soft definitions.