Consensus of state of the art mortality prediction models: From
  all-cause mortality to sudden death prediction
Yola Jones Fani Deligianni Jeff Dalton Pierpaolo Pellicori John G F Cleland
Worldwide, many millions of people die suddenly and unexpectedly each year,
either with or without a prior history of cardiovascular disease. Such events
are sparse (once in a lifetime), many victims will not have had prior
investigations for cardiac disease and many different definitions of sudden
death exist. Accordingly, sudden death is hard to predict.
  This analysis used NHS Electronic Health Records (EHRs) for people aged
$\geq$50 years living in the Greater Glasgow and Clyde (GG\&C) region in 2010
(n = 380,000) to try to overcome these challenges. We investigated whether
medical history, blood tests, prescription of medicines, and hospitalisations
might, in combination, predict a heightened risk of sudden death.
  We compared the performance of models trained to predict either sudden death
or all-cause mortality. We built six models for each outcome of interest: three
taken from state-of-the-art research (BEHRT, Deepr and Deep Patient), and three
of our own creation. We trained these using two different data representations:
a language-based representation, and a sparse temporal matrix.
  We used global interpretability to understand the most important features of
each model, and compare how much agreement there was amongst models using Rank
Biased Overlap. It is challenging to account for correlated variables without
increasing the complexity of the interpretability technique. We overcame this
by clustering features into groups and comparing the most important groups for
each model. We found the agreement between models to be much higher when
accounting for correlated variables.
  Our analysis emphasises the challenge of predicting sudden death and
emphasises the need for better understanding and interpretation of machine
learning models applied to healthcare applications.