Cardiovascular

Development of an interpretable machine-learning model to predict insufficient functional improvement after aquatic therapy in stroke.

TL;DR

A Random Forest model using pretreatment clinical data and initial rehabilitation/aquatic-therapy plans predicted insufficient motor improvement (ΔFMA <10) after aquatic therapy in stroke with temporal-validation AUC 0.818, and adding actual day-14 treatment-execution data did not improve prediction; external validation and prospective clinical-impact evaluation are required before clinical use.

Key Findings

About one-third of stroke patients in this single-center cohort had insufficient motor improvement after aquatic therapy.

  • 1,320 patients were included, of whom 409 had insufficient FMA improvement (ΔFMA <10 points at day 56 ± 7 days).
  • Total FMA was recalculated as upper-extremity plus lower-extremity FMA scores.
  • The development set (January 2022–December 2024) had 786 patients and 241 events; the temporal validation set (January–December 2025) had 534 patients and 168 events.

Random Forest was the best-performing model for Model A (baseline plus initial treatment plan) in temporal validation, with good discrimination.

  • AUC was 0.818 (95% CI 0.777-0.853) and Brier score was 0.172 (95% CI 0.160-0.186).
  • Model A used baseline clinical information and initial rehabilitation and aquatic-therapy plans available before the first aquatic session.
  • ExtraTrees, Random Forest, XGBoost, logistic regression and K-nearest neighbors were compared.

At a frozen sensitivity-prioritized threshold, Model A had high sensitivity and negative predictive value but modest specificity and PPV.

  • Threshold was 0.408.
  • Accuracy 0.700, sensitivity 0.857, specificity 0.628.
  • Positive predictive value 0.514, negative predictive value 0.906, F1 score 0.643.

Adding actual treatment-execution parameters accumulated through day 14 (Model B) did not improve prediction over Model A.

  • Random Forest was also best for Model B with AUC 0.814 (95% CI 0.774-0.850) and Brier score 0.174 (95% CI 0.163-0.186).
  • The paired change in AUC was -0.004 (95% CI -0.022 to 0.014).
  • Landmark window for day 14 was days 12-16.

SHAP analysis of Model A identified planned aquatic-therapy parameters, baseline motor function and time since stroke as the most important predictors.

  • Top predictors were planned aquatic-course duration, planned weekly aquatic frequency, baseline FMA-LE, baseline upper-extremity FMA and time from stroke onset to rehabilitation.
  • Model interpretability was assessed with Shapley additive explanations.

Model B illustrates how risk could be updated at day 14 once real execution records are available, but the study does not show that model-guided adjustment improves recovery.

  • Model A used routine data available before the first aquatic session and was evaluated in a later cohort from the same center.
  • The authors state these analyses do not show that model-guided treatment adjustment improves motor recovery.
  • External validation and prospective clinical-impact evaluation are required before clinical use.

The study used temporal validation and multiple evaluation approaches beyond discrimination.

  • Training on 2022-2024 cases and validation on 2025 cases.
  • Performance assessed using AUC, calibration, decision-curve analysis (DCA) and SHAP.
  • Single-center retrospective design in a Department of Rehabilitation Medicine.

What This Means

This study built computer models to predict which stroke patients are unlikely to gain meaningful motor recovery (a gain of fewer than 10 points on the Fugl-Meyer scale) after about eight weeks of aquatic therapy. Using records from 1,320 patients at one hospital, about 31% had insufficient improvement. A Random Forest model that used information available before the first pool session, such as baseline motor scores, time since stroke, and the planned length and frequency of aquatic therapy, identified these patients fairly well when tested on a later group of patients (AUC 0.818). At the chosen cutoff, the model caught most patients who would not improve enough (sensitivity about 86%) and was usually right when it said someone was low-risk (about 91%). However, about half of those flagged as high risk actually improved sufficiently. Adding data on the therapy actually delivered during the first two weeks did not make predictions better, though that version could in principle be used to update risk at day 14. This research suggests that routinely collected information could help flag patients who might need a different rehabilitation approach. However, the study was retrospective and from a single center, and it did not test whether using the model to change treatment improves recovery. The authors say external validation and prospective studies are needed before any clinical use.

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Citation

Chen Y, Zhang J, Qie S. (2026). Development of an interpretable machine-learning model to predict insufficient functional improvement after aquatic therapy in stroke.. Frontiers in neurology. https://doi.org/10.3389/fneur.2026.1871732