As Fitbits, which monitor basic body movement and heart rate, have been growing in popularity, it’s no surprise that people are also turning to smart phone apps to track other health measures like high blood pressure. After all, people with hypertension are told to routinely monitor their blood pressure at home, and the old blood pressure cuff monitor is bulky, expensive and slow (at least compared to an app).
In fact, blood pressure apps are hot sellers. The Instant Blood Pressure app, which boasted a no-cuff reading in its ad copy, was a top 50 best selling iPhone app for more than 150 days.
But buyer beware. A new study from Johns Hopkins University School of Medicine warns patients with hypertension not to rely on apps to test your blood pressure. The study, published online in JAMA Internal Medicine, found that the Instant Blood Pressure app was completely wrong eight out of 10 times in people with high blood pressure. The app showed that their pressure was in the normal range, when a standard cuff monitor found that it was high. Systolic blood pressure readings were within 5 mm Hg of the measurements taken by a cuff only 24 percent of the time, and within 10 mmHg 44 percent of the time.
The app was recently taken off the market, perhaps because of a cautionary review in iMedicalapps.com, but it was widely downloaded, and there are many others that work just like it and still available.
“Because this app does such a terrible job measuring blood pressure,” says Timothy B. Plante, MD, a fellow in the division of general internal medicine at the Johns Hopkins University School of Medicine. “It could lead to irreparable harm by masking the true risk of heart attacks and strokes in people who rely on the accuracy of this information.”
The apps come up with their readings in different ways. For the Instant Blood Pressure app, you put your finger on the camera (presumably to measure your heart rate) and put the phone’s microphone on your heart (to record the beat). Blood pressure has nothing to do with heart beat. “Before using it, it asks you to enter your date of birth, sex, height and weight, so my suspicion is that the number it spits out is an estimate of what it should be based on those factors,” says Dr. Plante.
“The most concerning thing for me is that it missed the hypertensive measurements four out of five times,” says Dr. Plante. “I’m concerned about the silent killer of hypertension. We need to identify it, to treat it and mitigate its effects, because it can lead to heart problems, kidney disease, and stroke.”
In fact, companies would get in trouble with the Food and Drug Administration if they were selling a health device that was not approved, so many companies put disclaimers on their apps, saying that the apps should just be used for entertainment, not health purposes. But it’s clear, based on the comments on the app pages, that people are using them for their health.
“We think there is definitely a role for smart phone technology in health care, but because of the significant risk of harm to users who get inaccurate information, the results of our study speak to the need for scientific validation and regulation of these apps before they reach consumers,” says Dr. Plante.
On the other hand, Dr. Plante finds apps that help people record information such as blood pressure and glucose readings invaluable. “I heavily encourage my patients to use activity trackers, diet trackers and health trackers,” he says. “I love to see people bring in their data on their phones.”