Set your smartwatch alarm. You’re about to be barraged by tons of hype about the health benefits of the Apple Watch. Unfortunately, it won’t include essential information and data that can put these claims in proper perspective.
Last year, Apple CEO Tim Cook tweeted how an Apple Watch detected a rapid heartbeat in an 18-year-old girl, who said the device saved her life. Now, with the presentation on Saturday of findings from an enormous Apple Watch study at the American College of Cardiology meeting in New Orleans, the hype meter is about to go to 11.
Stories like Deanna’s inspire us to dream bigger and push harder every day. https://t.co/O7xJ9n1MHg
— Tim Cook (@tim_cook) May 1, 2018
The Apple Heart Study, conducted by Stanford University researchers and sponsored by Apple, evaluated the ability of the Apple Watch to detect atrial fibrillation, a common heart disorder also known as A-fib, in an astonishing 400,000 participants.
A-fib affects somewhere between 3 million and 6 million Americans, most of them over age 65. In some people it’s silent, causing no symptoms. In others it causes heart palpitations, dizzy spells, and shortness of breath. Whether or not a-fib causes symptoms, it quadruples the risk of having a stroke.
While the Apple Heart Study will tell us many new things about the watch, what it won’t do — what it can’t do — is provide any insight into the device’s real overall effects on health. This is because the study was not a randomized controlled trial, the gold standard of medical research.
Instead, it is a purely observational study designed to see whether the Apple Watch’s heart pulse monitor can identify people who have a-fib. But because the study does not contain a control arm, it can’t say what might have happened to a similar group of 400,000 people who did not use the Apple Watch. The study will therefore be a rich source of anecdotes but, as good scientists know, anecdotes aren’t data. (Just because your friend’s uncle got rich playing the lottery you shouldn’t conclude that it’s a good idea to spend your next paycheck on the lottery!)
Some people will inevitably argue that saving the life of a young girl, as related by the Apple CEO, is proof the watch can contribute to our health. But that assumption may not hold up if the cost of the benefit means harm to many other healthy people.
When evaluating a new drug or device, it is a cardinal rule that the benefits must be weighed against the risks. With some drugs and devices, the risks are obvious. In others, such as with something as apparently benign as the Apple Watch, the risks may be less immediately apparent. Nevertheless, they can be real and potentially significant.
To understand these potential harms, it’s important to recognize that no medical test is perfect. There are always false negatives, in which the device fails to detect a real problem, and false positives, in which it wrongly detects a problem that doesn’t exist.
Harm occurs from these in several ways. One is when people who have atrial fibrillation don’t consult a doctor about symptoms such as heart palpitations or shortness of breath because they feel falsely reassured by the absence of any alert from their Apple Watch. The new study provides no evidence about the true rate of false negatives in the study population because the researchers did not independently monitor people in whom the device did not detect a-fib.
A far more common problem will be false positives, in which the watch delivers an alert to people who do not have a-fib. Imagine the impact of such an alert on a perfectly healthy person who suddenly believes he or she might have a heart rhythm disorder. Then imagine the impact on a health care system as thousands of young, healthy people suddenly want to schedule appointments with cardiologists. Is this really the best use of time for those seeking care or those providing it? Can our already overburdened health care system absorb this sort of influx? What will happen to the underserved sick and elderly people who really do need the services of a cardiologist?
You may think it’s a mistake to focus on false positives and false negatives because the watch is highly accurate at detecting a-fib. But experts who have looked at this issue already know that there will be a large number of false positive alarms, far more than the number of accurate positive alarms. Venkatesh Murthy, a cardiologist at the University of Michigan who has studied this issue, told me that more than 90 percent of irregular rhythm alerts in younger and middle aged users will be false alarms.
Even if the Apple Watch does work correctly, it is by no means clear it will generate benefits to the public’s health. Most episodes of a-fib are not harmful. There has been an enormous amount of research on people with a-fib who enter the health care system through conventional means — most often by going to a doctor about their symptoms or by having the problem diagnosed during a physical examination. The medical community has a fairly good idea about which of these patients are most likely to benefit from further treatment, although I must acknowledge that there is some controversy even here.
But the medical community has no idea how to respond appropriately or efficiently to the large number of people who will be identified as having a-fib by the Apple Watch alone. Most of these people — young and tech-savvy — will almost certainly be at low risk for a stroke or other harmful consequence of a-fib. It is entirely possible that the vast majority would do fine until their heart problem was identified by traditional means.
It is also possible that the harms of the treatments they are offered could outweigh any reduction in stroke risk. In fact, the blood-thinning drugs used to prevent stroke in people with a-fib can make it difficult to stop bleeding and can even lead to an uncommon but serious kind of stroke caused by bleeding into the brain.
There no evidence yet that treating people for a-fib that’s first detected by an Apple Watch will result in a net benefit when strokes averted are balanced against excessive bleeding and complications from procedures for a-fib like catheter ablation or the implantation of a Watchman device. And the Apple Heart Study will not provide this proof.
There’s a lot of enthusiasm out there for new, high-tech devices like the Apple Watch, but it is extremely difficult to find thoughtful perspectives on the complex medical issues they raise. We are in the middle of an overwhelming rush to embrace new technology and make health data available to everyone. This movement is fueled by Apple and other technology companies that are starting to spread some of their enormous wealth in the medical community, laying the groundwork for their expansion into this field.
Unfortunately the immediate response to this new study is likely to be even more irrational exuberance and premature implementation of a potentially harmful technology before there is any evidence showing that the Apple Watch actually improves human health.
Larry Husten writes the CardioBrief blog.