What wearables and digital biomarkers add to how we measure health

Tens of millions of people now carry devices that count steps, measure heart rate and estimate sleep continuously, and large cohorts — UK Biobank's accelerometer sub-study, the All of Us programme, several national cohorts — have begun to link those signals to outcomes. The early findings are strong and simple: step counts and measured activity predict mortality better than questionnaires, and the relationship is graded down to low levels of activity. Beyond that the evidence is mixed. Whether continuous monitoring improves outcomes when acted on has been tested mostly in single conditions with modest results; the populations that wear devices are healthier and richer than those that do not, which limits what can be generalised; and the measures themselves — sleep staging, heart-rate variability — are validated unevenly. For population statistics the question is whether device data can supplement surveys of physical activity and health, and the offices are only beginning to ask it.

Status

emerging

Direction

mixed

Would change our view

A population-representative cohort with device data and mortality follow-up; or a trial in which monitoring changed a hard outcome at scale.

Trackers

Gaps

Representative samples rather than volunteers; device data from Japan, Korea and the Nordic countries linked to registers; validation of the derived measures against clinical ones.