New research suggests that an Apple Watch feature designed to identify signs of high blood pressure should not be used as a substitute for regular medical screening tests.
Experts warn against relying on the device for health alerts, citing the potential for “false reassurance,” and stress that individuals must continue to undergo regular blood pressure checks using a traditional cuff.
Apple itself states that its “hypertension (high blood pressure) notifications feature” is “not intended to diagnose, treat or aid in the management of hypertension or other conditions such as blood clots, stroke, atrial fibrillation, congestive heart failure or high cholesterol.”
The company further clarifies that the Apple Watch cannot detect heart attacks, and not all individuals with high blood pressure will receive a notification.
Instead, the feature’s purpose is to identify patterns of chronic high blood pressure, utilising a heart sensor and a 30-day evaluation period.
In the new study, researchers from the University of Utah Health and the University of Pennsylvania, noted that the US Food and Drug Administration approved the Apple Watch hypertension feature for use last year.
Writing in the Journal of the American Medical Association, the researchers looked at Apple’s own data and examined what the real-world impact of this technology might look like.
“According to Apple’s reported test performance, 41.2% of individuals with undiagnosed hypertension would receive an alert for potentially having hypertension, and 58.8% would not,” the researchers said.
“Among those without hypertension, 92.3% would not receive an alert and 7.7% would receive an inappropriate alert.”
The results suggest “moderate evidence to rule in hypertension” and “weak evidence to rule out hypertension”, they said.
Analysis in the real-world by the team suggested that the absence of an alert is more reassuring in younger adults and substantially less reassuring in older adults, who are more likely to suffer high blood pressure.
The team concluded: “With more than 200 million Apple Watch users worldwide, the hypertension notification feature offers new opportunities to identify adults with undiagnosed hypertension, but with potential for hypertension misclassification as well.
“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.
“Apple indicates that the feature is not intended to diagnose hypertension and is designed to prompt users to seek clinical evaluation if hypertension is suspected.
“However, false reassurance may discourage some individuals with undiagnosed hypertension from obtaining appropriate screening or engaging with the healthcare system, resulting in missed opportunities for early detection and treatment.”
The team said limitations include reliance on Apple’s sensitivity and specificity estimates, “which may not fully capture device performance”.
In an editorial on the issue, experts including from the Harvard school of public health in Boston, wrote: “The main caveat of the hypertension notification feature’s intention to screen for hypertension is that 59% of individuals with undiagnosed hypertension wearing the Apple Watch will not be alerted.
“Given that screening tests are expected to be good at ruling out a disease, the absence of a notification could lead to false reassurance, deferred care, and delayed diagnosis.
“Thus, the hypertension notification feature’s current performance is not suitable for large-scale, reliable hypertension screening.”
Apple has been contacted for comment.
Professor Bryan Williams, chief scientific and medical officer at the British Heart Foundation (BHF), said: “High blood pressure is known as the silent killer for good reason, as it is usually symptomless.
“Untreated, high blood pressure contributes to tens of thousands of preventable heart attacks and strokes in the UK each year.
“It’s estimated that up to five million people in the UK are living with undiagnosed high blood pressure.
“We need more opportunities for people to get their blood pressure checked quickly and easily to avoid more preventable heart attacks and strokes.
“Smart tech like this can be useful for people who want to keep a closer eye on various aspects of their health.
“The potential to alert about possible hypertension will also prompt wearers of this technology to get their blood pressure formally checked.
“But this analysis makes it clear that we should not rely on this type of wrist-worn technology alone to warn us if we have high blood pressure, as most people with undiagnosed high blood pressure in this analysis would not have received an alert.
“It’s crucial that people understand that this technology is not a replacement for getting your blood pressure checked with standard cuff-based devices.”
