Research testing the real world impact of the newly FDA approved Apple Watch hypertension alert shows receiving an alert is a useful push for people to get further screening, but the overall accuracy could be better.
A previously published validation study of the Apple alert suggested 41.2% of people with undiagnosed hypertension would receive an alert for potentially having the condition and 58.8% would not. Â In those without hypertension, the study predicted 92.3% would not receive an alert and 7.7% would receive an inappropriate alert.
“With more than 200 million Apple Watch users worldwide, the hypertension notification feature offers opportunities to identify adults with undiagnosed hypertension but with potential for hypertension misclassification as well,” write lead author Jordana Cohen, MD, University of Pennsylvania, and colleagues.
“A large proportion of individuals unaware of their hypertension may be made aware. However, an even larger proportion of individuals with undiagnosed hypertension could receive no alert at all,” they caution.
Smart watches developed by Apple, Samsung and Fitbit have received FDA approval for  atrial fibrillation alerts over the last few years, but last September Apple was the first to get a hypertension alert cleared by the FDA.
Hypertension is very common in the U.S. and is estimated to affect more than half of all adults over the age of 50 years. While it is often asymptomatic in the short term, it is a leading cause of heart attacks, stroke, heart failure, and kidney disease, and also contributes to dementia and cognitive decline.
While many people receive treatment for high blood pressure, almost half of individuals with hypertension do not know they have it and are not being treated for it, which has prompted the development of the smartwatch alert.
As reported in JAMA, Cohen and colleagues carried out a modeling study based on validation data from Apple and also from the National Health and Nutrition Examination Survey (NHANES) 2017–2020 to estimate how accurate the Apple alert would be versus standard home blood pressure monitoring over 30 days.
The team took existing blood pressure data from NHANES 2017–2020, a large, ongoing U.S. health survey. They included data from participants aged 22 years or older, who were not pregnant, had no known high blood pressure, and were not on blood pressure medication. They then used Apple’s previously reported sensitivity and specificity data for the hypertension notification and mathematically applied it to the NHANES population.
In the estimated scenario using NHANES data, the researchers found that if people received a high blood pressure alert from their watch, there was about a 70% chance that they really did have hypertension and about a 30% chance it was a false alarm.
In contrast, when people did not get a high blood pressure alert the team estimated there was a 79% chance that they did not have hypertension, but still about a 21% chance that Apple Watch wearers had the condition even though they weren’t alerted.
“The manufacturer indicates that the feature is not intended to diagnose hypertension and is designed to prompt users to seek clinical evaluation if hypertension is suspected,” concede the authors.
“However, false reassurance may discourage some individuals with undiagnosed hypertension from obtaining appropriate screening or engaging with the health care system, resulting in missed opportunities for early detection and treatment,” they warn.
The authors suggest further validation, improved accuracy of the alert and suitable integration into population screening could make the cuffless hypertension feature more useful on a wider scale.
