The Apple Watch is increasingly positioned as a tool for population-level health screening. In September 2025, the U.S. Food and Drug Administration cleared Apple’s Hypertension Notifications Feature, which uses optical sensors to analyze blood flow patterns and alert users when their data suggest possible high blood pressure. The feature is explicitly not intended to diagnose hypertension, but to prompt users to seek further evaluation.
A new study published in the Journal of the American Medical Association now provides insight into what the real-world impact of this technology could be. Researchers from the University of Utah and the University of Pennsylvania analyzed how Apple Watch alerts might perform if widely used among U.S. adults with undiagnosed hypertension.
“High blood pressure is what we call a silent killer,” said Adam Bress, Pharm.D., M.S., senior author and researcher at the Spencer Fox Eccles School of Medicine at the University of Utah. “You can’t feel it for the most part. You don’t know you have it. It’s asymptomatic, and it’s the leading modifiable cause of heart disease.”
Variable performance across populations
Earlier validation work by Apple showed that around 59% of people with undiagnosed hypertension would not receive an alert, while approximately 8% of people without hypertension would receive a false alert. Building on this, the new analysis used data from a nationally representative U.S. health survey to estimate how these alerts would change the likelihood that a user actually has hypertension.
The researchers focused on adults aged 22 years and older who were not pregnant and were unaware of having high blood pressure. This is the population eligible to use the feature. Their findings show that the value of an alert, or the lack of one, varies substantially by age and other demographic factors.
Among adults younger than 30, receiving an alert increased the probability of having hypertension from 14% to 47%, while not receiving an alert reduced it slightly to 10%. In contrast, for adults aged 60 and older, who have a much higher baseline prevalence of hypertension, an alert increased the probability from 45% to 81%. Importantly, the absence of an alert in this group still left a 34% likelihood of hypertension.
The same pattern was seen across racial and ethnic groups. Among non-Hispanic Black adults, an alert increased the probability of hypertension from 36% to 75%, while no alert lowered it to 26%. For Hispanic adults, the probability rose from 24% to 63% with an alert and fell to 17% without one. According to the researchers, these differences reflect broader disparities in cardiovascular health driven largely by social determinants of health.
Supplement, not a replacement
With an estimated 30 million Apple Watch users in the U.S. and around 200 million worldwide, the authors stress that smartwatch alerts should complement, not replace, established screening methods. “If it helps get people engaged with the health care system to diagnose and treat hypertension using cuff-based measurement methods, that’s a good thing,” Bress said.
Current guidelines recommend regular blood pressure screening with validated cuff-based devices, particularly for adults aged 40 and older. The researchers caution that not receiving a smartwatch alert could give users a false sense of reassurance, potentially delaying appropriate testing and treatment. For patients that receive an Apple Watch alert, Bress advises clinicians to perform “a high-quality cuff-based office blood pressure measurement” and to confirm results with home or ambulatory monitoring when appropriate.
The research team plans further studies to estimate how many people might receive false-negative or false-positive alerts, taking into account regional and socioeconomic differences.
