Set your smartwatch alarm. You’re about to be barraged by tons of hype about the health benefits of the Apple (AAPL) 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.

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.

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  • 1. About the author? An email address and a twitter address. That tells me a lot.
    2. Personal experience with AFib? Unknown.
    3. Does he know that the biggest problem people with Afib have is getting a diagnosis of Afib?

    I have lived with Afib for over 40 years as did my mother, father and grand-mother. Maybe having your first (or ANY) episode of Afib while in a cardiologist’s office during the 30 seconds you are actually recording on the 12 lead EKG it took you hours, weeks, months, YEARS to get hooked up to is the gold standard but it rarely (never) happens that way. These wearable monitors are godsends. Now you can “see” what you have only been feeling and struggling to describe before, AND you can show it to others and they can see it too. If it matches what you most likely have been feeling it is probably accurate. If it is an anomaly you probably already know that, too. If it isn’t it won’t take you 5, 10 or even 20 years to have a doctor see it. Catching most afib is like seeing the end of a rainbow…and no one getting it unless you can show them the pot of gold. Or, more accurately, no one being able to know exactly what you saw/felt, and what to do about it, unless and until they can see it too. I found this article looking for info about the Apple watch. I already have a Kardia 6 lead device and use CardioDiagnosis app on my phone. I am considering an ablation. I read a study that said the continuous wear devices are “a great new tool for the PROPER ASSESSMENT of your afib. A godsend for me. I know what I feel without any doubt. When it starts, when it stops, how bad it is. But I could not show it to a cardiologist/electrophysiologist, to anyone, before these devices came along. As for one Apple watch recording of one episode of afib instantly putting you on lots of dangerous, expensive and in the case of afib, probably ineffective and/or unsustainable drugs and or procedures, that is no more likely than… one above average blood glucose result or one high blood pressure reading doing the same. And if it does, you need at least a second opinion and at best another doctor. Should we throw out all the blood pressure monitors, all the blood sugar monitors, all the blood tests, urinalyses, xrays, ultrasounds, MRIs, C125s because some are false positives, false negatives, unclassified or unclassifiable? It is a tool. Useful for amateurs and experts alike.

  • This article is as detrimental as the claims of incomplete (and proposed harmful) affects of the subject – the Apple Watch. The article is full of negative claims and proposes, generally, that because the cardio measurement features of the watch are not always beneficial, that the interest in the watch is hype. I don’t think so.

    Since being introduced, I have used the watch and associated application to measure and watch for Afib. I have had intermittent Afib many times in my life and I know what to watch for and how to detect it / validate it. The watch, for me, is a convenience and has never missed. Now I realize that is a subjective statement. But Husten works very hard in the article to state that the metrics of the watch’s use are not concise and complete, and thus are flawed. If so, then Husten would be unable to make the negative claims he makes throughout the article. If you can’t validate a positive, you equally cannot validate a negative.

    It is nonsensical articles like this, based on the author’s own style of hype, that causes solid and meaningful technology to take years and years of repeating studies to finally be released to the public. Lives are impacted during that time. (I fully support reasonable and meaningful validative studies, but the FDA and similar organizations, along with articles like this one, hinder and slow good – even great – technologies, medications, and other healthcare benefits from the general public).


  • Is Apple assuming you’re going to be wearing the watch 24/7? Last time I checked, A fib has a crazy attribute of being rather intermittent and kinda random. What if you’re not wearing the watch, oh I dont know, like 16 hrs a day, or let’s be crazy, 1 hr, while you’re showering and getting ready for work. Does A fib kinda wait for you to put the watch on? Respectfully stated.

    • That doesn’t mean it’s useless technology. And furthermore, yes they expect you to wear it in the shower, it’s waterproof. And has all-day battery life and doesn’t take very long at all to charge up. You could even wear it while sleeping if you wanted to, although that might be the ideal time to charge it due to your claim that a-fib could spur up at any moment

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