Reliability of Supervised Machine Learning Using Synthetic Data in Health Care: Model to Preserve Privacy for Data Sharing

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Background: The exploitation of synthetic data in health care is at an early stage. Synthetic data could unlock the potential within health care datasets that are too sensitive for release. Several synthetic data generators have been developed to date; however, studies evaluating their efficacy and generalizability are scarce.

Objective: This work sets out to understand the difference in performance of supervised machine learning models trained on synthetic data compared with those trained on real data.

Methods: A total of 19 open health datasets were selected for experimental work. Synthetic data were generated using three synthetic data generators that apply classification and regression trees, parametric, and Bayesian network approaches. Real and synthetic data were used (separately) to train five supervised machine learning models: stochastic gradient descent, decision tree, k-nearest neighbors, random forest, and support vector machine. Models were tested only on real data to determine whether a model developed by training on synthetic data can used to accurately classify new, real examples. The impact of statistical disclosure control on model performance was also assessed.

Results: A total of 92% of models trained on synthetic data have lower accuracy than those trained on real data. Tree-based models trained on synthetic data have deviations in accuracy from models trained on real data of 0.177 (18%) to 0.193 (19%), while other models have lower deviations of 0.058 (6%) to 0.072 (7%). The winning classifier when trained and tested on real data versus models trained on synthetic data and tested on real data is the same in 26% (5/19) of cases for classification and regression tree and parametric synthetic data and in 21% (4/19) of cases for Bayesian network-generated synthetic data. Tree-based models perform best with real data and are the winning classifier in 95% (18/19) of cases. This is not the case for models trained on synthetic data. When tree-based models are not considered, the winning classifier for real and synthetic data is matched in 74% (14/19), 53% (10/19), and 68% (13/19) of cases for classification and regression tree, parametric, and Bayesian network synthetic data, respectively. Statistical disclosure control methods did not have a notable impact on data utility.

Conclusions: The results of this study are promising with small decreases in accuracy observed in models trained with synthetic data compared with models trained with real data, where both are tested on real data. Such deviations are expected and manageable. Tree-based classifiers have some sensitivity to synthetic data, and the underlying cause requires further investigation. This study highlights the potential of synthetic data and the need for further evaluation of their robustness. Synthetic data must ensure individual privacy and data utility are preserved in order to instill confidence in health care departments when using such data to inform policy decision-making.
Original languageEnglish
Article numbere18910
Pages (from-to)1-21
Number of pages21
JournalJMIR Medical Informatics
Issue number7
Publication statusPublished (in print/issue) - 20 Jul 2020

Bibliographical note

Funding Information:
The MIDAS Consortium gratefully acknowledges the support to this project from the European Union research fund Big Data Supporting Public Health Policies under grant agreement No. 727721 (H2020-SC1-2016-CNECT SC1-PM-18-2016). We also acknowledge the support of the eHealth & Data Analytics Dementia Pathfinder Programme and Health and Social Care Board eHealth Directorate for this work under award ER/DARUG/09/18/10S.

Publisher Copyright:
© 2020 Debbie Rankin, Michaela Black, Raymond Bond, Jonathan Wallace, Maurice Mulvenna, Gorka Epelde.

Copyright 2020 Elsevier B.V., All rights reserved.


  • synthetic data
  • supervised machine learning
  • data utility
  • health care
  • decision support
  • statistical disclosure control
  • privacy
  • open data
  • stochastic gradient descent (SGD)
  • Decision tree
  • k-Nearest neighbor
  • Random forest
  • support vector machine


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