Machine-Learning Based Model to Improve Insulin Bolus Calculation in Type 1 Diabetes Therapy

Objective: This paper aims at proposing a new machine-learning based model to improve the calculation of mealtime insulin boluses (MIB) in type 1 diabetes (T1D) therapy using continuous glucose monitoring (CGM) data. Indeed, MIB is still often computed through the standard formula (SF), which does not account for glucose rate-of-change ( $\Delta$ G), causing critical hypo/hyperglycemic episodes. Methods: Four candidate models for MIB calculation, based on multiple linear regression (MLR) and least absolute shrinkage and selection operator (LASSO) are developed. The proposed models are assessed in silico , using the UVa/Padova T1D simulator, in different mealtime scenarios and compared to the SF and three $\Delta$ G-accounting variants proposed in the literature. An assessment on real data, by retrospectively analyzing 218 glycemic traces, is also performed. Results: All four tested models performed better than the existing techniques. LASSO regression with extended feature-set including quadratic terms (LASSO $_Q$ ) produced the best results. In silico, LASSO $_Q$ reduced the error in estimating the optimal bolus to only 0.86 U (1.45 U of SF and 1.36–1.44 U of literature methods), as well as hypoglycemia incidence (from 44.41% of SF and 44.60–45.01% of literature methods, to 35.93%). Results are confirmed by the retrospective application to real data. Conclusion: New models to improve MIB calculation accounting for CGM- $\Delta$ G and easy-to-measure features can be developed within a machine learning framework. Particularly, in this paper, a new LASSO $_Q$ model was developed, which ensures better glycemic control than SF and other literature methods. Significance: MIB dosage with the proposed LASSO $_Q$ model can potentially reduce the risk of adverse events in T1D therapy.