BioStress-AI: An Intelligent Recognition System for Physiological Stress Based on Heart Rate Variability and Machine Learning

BioStress-AI is a system that uses Heart Rate Variability (HRV) data and machine learning technology to achieve automatic classification of cognitive stress states. It aims to solve the problem that traditional stress assessment relies on subjective questionnaires or expensive equipment, making daily continuous monitoring difficult, and explores its potential application value in intelligent healthcare and wearable devices. Its core uses the Random Forest algorithm and builds an end-to-end classification model based on the SWELL HRV dataset, providing a technical foundation for stress monitoring.

This project was developed by Valeria Martinez Ramirez. Its scientific principle is based on the physiological mechanism of the Autonomic Nervous System (ANS) and stress response: when stressed, the sympathetic nerve is activated, heart rate increases, and HRV decreases; when relaxed, the parasympathetic nerve dominates, and HRV increases. It uses the public SWELL HRV dataset, which contains HRV-related indicator data for three states: no stress, interruption interference, and time pressure.

Feature Engineering

Selected multi-dimensional HRV features such as heart rate (HR), RMSSD (Root Mean Square of Successive Differences), SDRR (Standard Deviation of RR Intervals), LF/HF ratio, pNN50, and total power.

Exploratory Data Analysis

Used box plots and violin plots to show the distribution differences of indicators under different stress levels, correlation heatmaps to identify feature associations, and logarithmic transformation to improve data distribution.

Model Construction

Used a Random Forest classifier. The process includes data preprocessing (missing value handling, standardization), training-test set division, model training, and performance evaluation (accuracy, precision, recall, F1 score).

Performance: The Random Forest model achieved high classification accuracy on the test set, verifying the effectiveness of HRV as a stress biomarker. Feature Importance: HR contributed the most, while RMSSD (parasympathetic nerve indicator) and SDRR (overall heart rate variability) were key predictors. Physiological Insights: The LF/HF ratio was higher under time pressure; RMSSD and pNN50 were highly correlated (both reflect parasympathetic activity); the LF/HF ratio was positively correlated with HR (heart rate increases when sympathetic nerves are activated).

Potential application directions:

• Real-time stress monitoring: Deployed on wearable devices to track and alert high-stress states around the clock;
• Workplace health management: Group stress monitoring to optimize work processes;
• Clinical auxiliary diagnosis: Auxiliary diagnosis and treatment evaluation of anxiety and depression;
• Intelligent health applications: Personalized stress management interventions (breathing exercises, meditation guidance);
• Neurological disease research: Analysis of autonomic dysfunction (e.g., Parkinson's disease).

Challenges and improvements:

• Individual differences: Introduce personalized calibration or transfer learning;
• Environmental interference: More refined feature engineering or deep learning models;
• Privacy ethics: Protect sensitive health data;
• Generalization ability: Collect diverse real-scenario data to improve model robustness.

BioStress-AI successfully combines HRV data and machine learning to achieve high-precision classification of cognitive stress, providing a technical foundation for intelligent stress monitoring systems. It is a model of cross-integration of biomedical engineering, physiological signal processing, and AI, providing a reference path for researchers and developers in the digital health field. It is expected to promote the development of personalized stress management solutions in the future.