The Safety Challenges of Deep Learning in Real-World Type 1 Diabetes Management

Blood glucose simulation allows the effectiveness of type 1 diabetes (T1D) management strategies to be evaluated without patient harm. Deep learning algorithms provide a promising avenue for extending simulator capabilities; however, these algorithms are limited in that they do not necessarily learn physiologically correct glucose dynamics and can learn incorrect and potentially dangerous relationships from confounders in training data. This is likely to be more important in real-world scenarios, as data is not collected under strict research protocol. This work explores the implications of using deep learning algorithms trained on real-world data to model glucose dynamics. Free-living data was processed from the OpenAPS Data Commons and supplemented with patient-reported tags of challenging diabetes events, constituting one of the most detailed real-world T1D datasets. This dataset was used to train and evaluate state-of-the-art glucose simulators, comparing their prediction error across safety critical scenarios and assessing the physiological appropriateness of the learned dynamics using Shapley Additive Explanations (SHAP). While deep learning prediction accuracy surpassed the widely-used mathematical simulator approach, the model deteriorated in safety critical scenarios and struggled to leverage self-reported meal and exercise information. SHAP value analysis also indicated the model had fundamentally confused the roles of insulin and carbohydrates, which is one of the most basic T1D management principles. This work highlights the importance of considering physiological appropriateness when using deep learning to model real-world systems in T1D and healthcare more broadly, and provides recommendations for building models that are robust to real-world data constraints.

Offline Reinforcement Learning for Safer Blood Glucose Control in People with Type 1 Diabetes

Hybrid closed loop systems represent the future of care for people with type 1 diabetes (T1D). These devices usually utilise simple control algorithms to select the optimal insulin dose for maintaining blood glucose levels within a healthy range. Online reinforcement learning (RL) has been utilised as a method for further enhancing glucose control in these devices. Previous approaches have been shown to reduce patient risk and improve time spent in the target range when compared to classical control algorithms, but are prone to instability in the learning process, often resulting in the selection of unsafe actions. This work presents an evaluation of offline RL as a means for developing clinically effective dosing policies without the need for patient interaction. This paper examines the utility of BCQ, CQL and TD3-BC in managing the blood glucose of nine virtual patients within the UVA/Padova glucose dynamics simulator. When trained on less than a tenth of the data required by online RL approaches, this work shows that offline RL can significantly increase time in the healthy blood glucose range when compared to the strongest state-of-art baseline. This is achieved without any associated increase in low blood glucose events. Offline RL is also shown to be able to correct for common and challenging scenarios such as incorrect bolus dosing, irregular meal timings and sub-optimal training data.