Smartwatch screening for hypertension

An analysis of 2021-2023 National Health and Nutrition Examination Survey (NHANES) data found that among nonpregnant adults with hypertension (defined as systolic blood pressure 130 mm Hg or higher, diastolic blood pressure 80 mm Hg or higher, or use of antihypertensive medication), nearly 80% had a mean of three blood pressure (BP) measurements higher than 130/80 mm Hg. Of this group with uncontrolled BP, based on some practice guidelines, fewer than 40% were taking antihypertensive medications. Although undertreatment of high BP may result from therapeutic inertia, many adults do not have a regular source of care and simply do not know that they have hypertension.

Identifying undiagnosed hypertension is the goal of the Apple Watch’s hypertension notification feature, which was cleared in September 2025 by the US Food and Drug Administration for use in nonpregnant people 22 years or older. The watch is not a substitute for a home BP monitor, and it does not provide individual BP measurements. Instead, it uses an optimal sensor that collects photoplethysmography (PPG) data during waking hours over 30-day intervals, analyzes that data with a machine-learning algorithm, and alerts the wearer if hypertension is suspected. The alert encourages patients to monitor their BP at home for 7 days and consult their doctor about next steps.

A clinical validation study involving more than 2,000 participants found that the Apple Watch correctly identified 214 of 585 people with BP of 130/80 mm Hg or higher (sensitivity = 41.2%) with a specificity of 92.3%. The alert’s positive and negative likelihood ratios were 5.35 and 0.64, respectively. In a research letter in JAMA, Dr. Jordana Cohen and colleagues applied the Apple Watch’s screening performance characteristics to the nationally representative NHANES population. The researchers calculated the posttest probabilities of hypertension after a positive or negative alert based on the prevalence of hypertension in different subgroups:

Among eligible individuals aged younger than 30 years, an alert increases the probability of hypertension from 0.14 (95% CI 0.11-0.17) to 0.47 (95% CI 0.39-0.56), wherein the absence of an alert lowers it to 0.10 (95% CI 0.07-0.12). Among individuals aged 60 years or older, an alert increases the probability of hypertension from 0.45 (95% CI 0.39-0.50) to 0.81 (95% CI 0.76-0.86) and the absence of an alert lowers it to 0.34 (95% CI 0.29-0.39).

Similar to the heart-rhythm monitoring and obstructive sleep apnea detection features of various wearable consumer devices, the Apple Watch’s hypertension screening feature may nudge some patients to seek appropriate care for an undiagnosed chronic condition. For others, it may cause unnecessary anxiety or provide false reassurance. Given the popularity of these devices, though, smartwatch screening for hypertension will become increasingly common.

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This post first appeared on the AFP Community Blog.