ResearchResearch paperLarge Language Models1 source · Oct 12, 2026

Sequence Composition in EHR Foundation Model Pretraining

Autoregressive electronic health record (EHR) foundation models predict the next event token in patient trajectories: sequences of structured medical events.

Key points

  • A typical pretraining strategy is to concatenate all trajectories into a global stream and sample token windows from it.
  • To explore this, we investigate how the composition of pretraining sequences affects clinical prediction performance.
  • Using the global-stream approach as a baseline, we propose alternative sequence composition methods that control how patient trajectories contribute to pretraining sequences.
  • Our results show that simply changing how EHR data are presented to the model during pretraining can improve downstream performance, without changing the model or collecting additional data.

Sources (1)

  • [1]Sequence Composition in EHR Foundation Model Pretraining
    arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 12, 02:41 PM
    Autoregressive electronic health record (EHR) foundation models predict the next event token in patient trajectories: sequences of structured medical events.
    A typical pretraining strategy is to concatenate all trajectories into a global stream and sample token windows from it.

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