Glucose‐lowering effects of physical activity in type 1 diabetes: A causal modelling and matched‐pair analysis approach

Aims To evaluate the acute glucose‐lowering effect of bouts of physical activity (PA) for hyperglycaemia in individuals with type 1 diabetes, using a within‐subject matched‐pairs causal design to approximate the control condition of no activity. Methods Data comprised 1546 PA bouts of 10–30 min from 482 participants in the T1DEXI and T1DEXIP cohorts where glucose was >10 mmol/L. Each PA bout was matched [starting glucose, glucose rate of change, insulin on board (IOB) and glucose variability (CV)] to a matched non‐PA period within the same individual using a weighted k‐nearest neighbours algorithm (SMD <0.01). Primary outcome: Change in glucose from PA onset to 20 min post‐activity. Secondary outcomes: Predictors of glucose response and rate of hypoglycaemia incidence. Results PA [median 23 min: IQR (20, 30)] led to a mean glucose change of −2.2 mmol/L ( p < 0.001), compared with 0.3 mmol/L ( p < 0.001) during matched non‐PA periods (mean difference: −1.9 mmol/L ( p < 0.0001)). No significant differences by age, activity type or intensity were observed. The strongest predictors of PA‐induced glucose change were (in order) glucose rate of change, starting glucose, CV, duration and IOB. A heatmap using starting glucose and glucose rate of change was developed to guide real‐time decision‐making. PA‐induced hypoglycaemia risk was very low (<2%). Conclusion/Interpretation Using PA to lower high glucose levels is an effective and safe strategy, and when guided by CGM, it can become a personalised tool for type 1 diabetes education.