Toward comprehensive multimodal health monitoring in heat: A digital biomarker exploration study

Background As climate is significantly changing, the need for effective physiological health monitoring during heat exposure becomes increasingly urgent. Population-based indices provide valuable environmental insights but fail to account for individual variability in heat response. A person-centered approach to heat strain assessment remains lacking. Digital biomarkers offer a promising avenue for individualized, continuous, and lab-independent health monitoring in real time. Here, we explored digital biomarker candidates for heat health monitoring. Methods We conducted a single-center, prospective, cross-sectional, cross-over, observational, explorative study to identify digital biomarker candidates for health management during heat exposure. 20 participants were exposed to various personalized heat stressors. Vital parameters, such as heart rate, core and close body temperature were assessed using wearable sensors, and the local sweat rate was determined using technical absorbents. A Random Forest model was built to distinguish between ambient temperature, relative humidity, and physical exertion through digital biomarker candidates. Results The Random Forrest model distinguished between the heat stressors with 94.7% accuracy. Key contributing variables differed by stressor type, highlighting the value of multimodal sensing including physiological and environmental factors. The variables distribution for each stressor revealed varying patterns: predictors for ambient temperature were primarily environmental measures, for exertion primarily physiological assessments, and relative humidity stressors physiological and environmental measures. Discussion Our findings reveal the potential of digital biomarkers to differentiate heat exposure origins and support the development of comprehensive automated, lab-independent, and person-centered health monitoring strategies. Further, this work showed the promise of integrating physiological as well as environmental measures to enable comprehensive health monitoring during heat exposure. Further testing is needed in more complex and real-life settings.