Smartwatch Health Data Accuracy Varies by Metric
A University of Michigan study finds smartwatches reliably track some health measures while others, such as sleep stages, are often inaccurate.
Updated on Nov. 3, 2026 in Sleep Disorders
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University of Michigan researchers published a study in the journal Sensors evaluating how accurately smartwatches measure health metrics. The work found step counts and resting heart rate are the most accurate under normal conditions, while total nightly sleep time is generally accurate.
Why it matters
About one-third of American adults use smartwatches to track health, so understanding which measurements can be trusted affects how people interpret their own data. The framework offers a way to judge what smartwatches collect and how they interpret it.
About one-third of American adults use smartwatches to track health metrics, according to the study's framing. Accuracy varies by measure, and proprietary algorithms mean results may not be comparable across brands.
The players
University of Michigan School of Kinesiology
The academic unit of the University of Michigan that developed the framework used to evaluate smartwatch data.
The details
Smartwatches combine signals from multiple sensors, including optical sensors that detect blood-flow changes at the wrist, and algorithms that produce estimates. The researchers say the data are most useful for tracking changes in the same person over time rather than comparing absolute values between devices.
Timeline
Study article published November 3, 2026.
Health Landscape
The study applies a University of Michigan School of Kinesiology framework to consumer smartwatches that about one-third of American adults use for health tracking. It separates reliable measures such as step counts and resting heart rate from less dependable outputs like sleep-stage estimates.
Smartwatch step counts and resting heart rate can be relied on for trend tracking, while nightly total sleep time is generally accurate. Sleep-stage readings such as REM and deep sleep may be unreliable and should be read cautiously.
The takeaway
Use smartwatch data mainly to spot changes in your own readings over time rather than to judge exact values. Treat total sleep duration as more dependable than detailed sleep-stage breakdowns.
Further reading
For related context on sleep tracking, explore Sleep Disorders coverage.
Source note: This article includes information reported by West Newsmagazine.
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