Background: Uptake of exercise in people with type 1 diabetes (T1D) is low despite significant health benefits. Fear of hypoglycemia is the main barrier to exercise. Continuous glucose monitoring (CGM) with predictive alarms warning of impending hypoglycemia may improve self-management of diabetes around exercise. Aim: To assess the impact of Dexcom G6 real-time CGM system with a predictive hypoglycemia alert function on the frequency, duration, and severity of hypoglycemia occurring during and after regular (≥150 min/week) physical activity in people with T1D. Methods: After 10 days of blinded run-in (Baseline), CGM was unblinded and participants randomized 1:1 to have the "urgent low soon" (ULS) alert switched "on" or "off" for 40 days. Participants then switched alerts "off" or "on," respectively, for a further 40 days. Physical activity, and carbohydrate and insulin doses were recorded. Results: Twenty-four participants (8 men, 16 women) were randomized. There was no difference in change from baseline of hypoglycemia <3.0 and <3.9 mmol/L with the ULS on or off during the 24 h after exercise. With ULS alert "on" time spent below 2.8 mmol/L compared with baseline was significantly (P = 0.04) lower than with ULS "off" in the 24 h after exercise. In mixed effects regression, timing of the exercise and baseline HbA1c independently affected risk of hypoglycemia during exercise; exercise timing also affected hypoglycemia risk after exercise. Conclusion: A CGM device with an ULS alert reduces exposure to hypoglycemia below 2.8 mmol/L overall and in the 24 h after exercise compared with a threshold alert.
Keywords: Continuous glucose monitoring; Exercise; Hypoglycemia; Type 1 diabetes.