Background: The advanced hybrid closed-loop (AHCL) algorithm combines automated basal rates and corrections yet requires meal announcement for optimal outcomes. We aimed to compare the performance of the MiniMed™ 780G AHCL algorithm with and without meal announcement. Methods: In a single-arm study involving 14 adults with type 1 diabetes, we evaluated the safety and efficacy of AHCL when meals were not announced. Participants stayed at a supervised environment for 5 days, during which the outcomes of not announcing meals (≤80 g of carbohydrate) were assessed. Next, participants entered a 90-day at-home "unannounced" phase, during which all meals (≤80 g of carbohydrate) were unannounced, followed by a 90-day at-home phase in which all meals were announced. Results: Time in range (TIR 70-180 mg/dL) was lower in the unannounced versus announced periods (67.5% ± 12.5% vs. 77.7% ± 9.5%; P < 0.01, respectively), with more time spent in hyperglycemia range 180-250 mg/dL (22.7% ± 7.7% vs. 15.7% ± 7.2%) and >250 mg/dL (7.9% ± 6.4% vs. 3.6% ± 2.7%), but less time in hypoglycemia range 54-70 mg/dL (1.6% ± 1% vs. 2.8% ± 1.8%) and <54 mg/dL (0.3% ± 0.4% vs. 0.7% ± 0.9%). Not announcing meals containing up to 60 g of carbohydrate did not lead to increase in postprandial extreme dysglycemia >250 mg/dL, and up to 20 g of unannounced carbohydrates did not significantly change the TIR 70-180 mg/dL compared with full announcement. Conclusion: The AHCL system is optimized for use with meal announcement. While not announcing meals of ≤80 g carbohydrates appears to be safe, it results in suboptimal postprandial glycemic control, especially with high-carbohydrate meals. Not announcing small meals (≤20 g carbohydrate) does not deteriorate glycemic control. Clinical Trial Registration number: NCT04479826.
Keywords: Automated insulin delivery; Closed-loop artificial pancreas; Meal announcement; Postprandial glycemia.