Digital Biomarker

A digital biomarker is a measurable, objective signal collected via a digital device, a wearable, a smartphone sensor, or an implant, that correlates with a physiological state or health outcome, where that correlation has been established through clinical research rather than assumed from the raw sensor output alone.

The distinction that separates a true digital biomarker from a general wellness metric is validation. A sensor producing a number is not automatically a biomarker. Resting heart rate qualifies as a digital biomarker because decades of clinical research have established what elevated or depressed resting heart rate means for cardiovascular and overall health outcomes. A proprietary composite score, a "readiness" or "strain" rating that blends multiple signals into one number, is not automatically a validated biomarker unless that specific composite has itself been studied against real clinical outcomes, independent of its individual inputs.

Digital biomarkers span a range of clinical maturity: well-established ones include resting heart rate trends and step count as an activity proxy; improving-but-imperfect ones include heart rate variability and sleep-stage classification; and early, less-validated ones include cuffless blood pressure estimation and wearable-derived stress or cortisol proxies. The category has grown substantially as AI and machine learning models have gotten better at extracting meaningful signal from noisy, continuous, real-world sensor data, rather than the periodic, controlled measurements clinical research traditionally relied on.