Biomedicine
A recovery score is still a long way from a health verdict
Eric Topol reshared his September essay questioning wearable HRV and readiness scores. Recording a signal, interpreting it and improving health are separate steps.
HRV describes variation between heartbeats. ECG records electrical activity; most consumer wearables infer variability from optical pulse signals. Topol argues that associations between low HRV and disease do not prove that raising it improves health. Readiness scores still lack validation against health outcomes.
A cited 2025 study measured 931 people at one medical institution for 5–7 seated minutes. The same upper-arm monitor recorded mean optical RMSSD of 37.49 milliseconds versus ECG’s 43.14. RMSSD measures successive normal beat-interval differences. These readings were not interchangeable.
The study did not test Apple Watch or follow health outcomes. Four authors worked for device maker Tiger Tech. It establishes a measurement concern, not an error estimate for every watch.
Topol challenges health claims, rather than all wearable functions. Scores across brands cannot be directly compared; a low score alone cannot establish deteriorating health.
Sources and further reading
Essay and study methods, tables, limitations and conflicts reviewed