Library / learning-module
Understanding wearable health technology
Audience: patients-public, students-learners ยท Review state: published
Measurement that moves with you
Wearable health technology is sensor technology worn on the body: smartwatches, fitness bands, rings, patches and smart clothing that measure heart rate, rhythm, movement, sleep, oxygen saturation and increasingly temperature and glucose.
The shift they represent is from measurement at appointments to measurement across real life, capturing patterns that a clinic visit cannot see.
What wearables measure well
Step counts and heart rate are the most mature measurements. Systematic reviews of commercial devices find step counting and resting heart rate generally reliable, while energy expenditure estimates are substantially less accurate, sometimes off by large margins.
Single-lead heart rhythm recordings from watches can flag possible atrial fibrillation, and several devices have regulatory clearance for that specific notification function.
Where caution applies
A wearable is a screening tool, not a diagnostic one. An irregular-rhythm notification means 'get this checked', not 'you have a diagnosis'; a normal reading does not clear symptoms that deserve care.
Accuracy varies by device, activity, skin tone, tattoos and fit, and sleep staging in particular is an estimate validated only loosely against laboratory sleep studies.
Making the data useful
The value of wearable data grows with context: trends over weeks matter more than single readings, and sharing selected trends with a clinician beats presenting raw logs.
Privacy deserves attention too: health data from consumer devices often sits outside medical confidentiality rules, governed instead by the manufacturer's policies. Reading the data-sharing settings before wearing is part of using the device.
Limitations
Educational overview of wearable health technology, not an evaluation of any specific product and not medical advice.