AbstractObjectiveTo predict older adults’ risk of avoidable hospitalization related to ambulatory care sensitive conditions (ACSC) using machine learning applied to administrative health data of Ontario, Canada.Design, Setting, and ParticipantsA retrospective cohort study was conducted on a large cohort of all residents covered under a single-payer system in Ontario, Canada over the period of 10 years, between 2008 and 2017. The study included 1.85 million Ontario residents between 65 and 74 years old at any time throughout the study period.Data sourcesAdministrative health data from Ontario, Canada obtained from the ICES Data Repository.Main outcome measuresRisk of hospitalizations due to ACSCs one year after the observation period.ResultsThe study used a total of 1,854,116 patients, split into train, validation, and test sets. The ACSC incidence rates among the data points were 1.1% for all sets. The final XGBoost model achieved an AUC of 80.5% on the held-out test set, and the predictions were well-calibrated. When ranking the predictions made by the model, those at the top 5% of risk as predicted by the model captured 37.4% of those presented with an ACSC-related hospitalization. A variety of features such as the previous number of ambulatory care visits, presence of ACSC-related hospitalizations during the observation window, age, rural residence, and prescription of certain medications were contributors to the prediction. Our model was also able to capture the geospatial heterogeneity of ACSC risk in the province of Ontario, and especially the elevated risk in rural and marginalized regions.ConclusionsThis study aimed to predict the 1-year risk of hospitalization from a series of ambulatory-care sensitive conditions in seniors aged 65 to 74 years old with a single, large-scale machine learning model. The model shows the potential to inform population health planning and interventions to reduce the burden of ACSC-related hospitalizations.