  Electronic Health Records (EHRs) are commonly used by the machine learning
community for research on problems specifically related to health care and
medicine. EHRs have the advantages that they can be easily distributed and
contain many features useful for e.g. classification problems. What makes EHR
data sets different from typical machine learning data sets is that they are
often very sparse, due to their high dimensionality, and often contain
heterogeneous (mixed) data types. Furthermore, the data sets deal with
sensitive information, which limits the distribution of any models learned
using them, due to privacy concerns. For these reasons, using EHR data in
practice presents a real challenge. In this work, we explore using Generative
Adversarial Networks to generate synthetic, heterogeneous EHRs with the goal of
using these synthetic records in place of existing data sets for downstream
classification tasks. We will further explore applying differential privacy
(DP) preserving optimization in order to produce DP synthetic EHR data sets,
which provide rigorous privacy guarantees, and are therefore shareable and
usable in the real world. The performance (measured by AUROC, AUPRC and
accuracy) of our model's synthetic, heterogeneous data is very close to the
original data set (within 3 - 5% of the baseline) for the non-DP model when
tested in a binary classification task. Using strong $(1, 10^{-5})$ DP, our
model still produces data useful for machine learning tasks, albeit incurring a
roughly 17% performance penalty in our tested classification task. We
additionally perform a sub-population analysis and find that our model does not
introduce any bias into the synthetic EHR data compared to the baseline in
either male/female populations, or the 0-18, 19-50 and 51+ age groups in terms
of classification performance for either the non-DP or DP variant.
