Researchers say modern smartwatches now track dozens of health metrics continuously, shifting them from fitness gadgets toward tools for early disease detection and personalized care.
Stanford studies found baseline changes in resting heart rate and heart-rate variability flagged more than 80% of infections before or at symptom onset, with signals appearing a median three days early.
Accuracy has improved for measures such as heart rate, blood oxygen and total sleep time, but sleep-stage classification matches lab EEG studies only about 70% of the time and can be overinterpreted.
The bigger obstacle is turning thousands of daily readings into clinically useful digital biomarkers that doctors can review, since most data remain siloed outside electronic health records.
Adoption still faces behavior, regulatory and privacy hurdles: one 471-person weight-loss trial found wearable users lost less weight, many features avoid FDA review as wellness tools, and consumer data often lack HIPAA protection.