339-OR: Timing of the Pre-exercise Temporary Target with Advanced Hybrid Closed-Loop (AHCL) and Hypoglycemia Risk

Aim: People with type 1 diabetes using hybrid closed loop (HCL) are advised to set a temporary elevated glucose target (TT) 1-2h pre-exercise. We aim to assess hypoglycemia risk with AHCL with TT set < 1h pre-exercise.

Method: To date 7 adults with type 1 diabetes using MiniMedTM 780g AHCL have completed 16 exercise bouts, including 40 min moderate intensity (MIE) at 50% VO2max in the morning (mMIE40) and evening (eMIE40); 90 min MIE at 50% VO2max in the evening (eMIE90]; and 40 min high intensity with 5×4min intervals at 90% VO2max in the evening (eHIE40). A TT (150mg/dL) was set: i) 1h prior [t60]; ii) 20min prior [t20]; iii) onset [t0]; iv) no TT [tNil]. For eMIE90 up to 45g supplemental CHO was given during exercise as per guidelines for exercise >60 min. CGM metrics were compared from exercise commencement to 2h post.

Results: For all TT conditions mean glucose with mMIE40 was higher than eMIE40 (7.9 [6.8, 9.3]mg/dL vs 6.5 [5.5, 7.2]mg/dL; p<0.05) with less time spent below 70mg/dL (0.0 [0.0, 0.0]% vs 6.3 [0.0, 13.3]%; p<0.001). Timing of initiating TT pre-exercise had minimal effect on glycemia with 40 min exercise while reducing hypoglycemia with 90min evening exercise (Table 1).

Conclusion: Supplemental CHO may be required for evening MIE of <60 min duration, while a TT set prior to long duration MIE in the evening reduces the risk of hypoglycemia. Morning MIE results in less time spent in hypoglycemia than evening MIE.