I believe, if you zoom out into the future, and you look back, and you ask the question, ‘What was Apple’s greatest contribution to mankind?’ it will be about health - Tim Cook
The Apple Watch has been quite successful as a smart watch. The company would also like it to succeed as a medical device. The recently published results of the Apple Heart Study in the New England Journal of Medicine show there’s still a long way to go.
An estimated six million people in the United States — nearly 2 percent — have atrial fibrillation, a type of irregular heartbeat that brings increased risk of events like clots, heart attacks and strokes. It’s thought that about 700,000 of people with the condition don’t know they have it.
A selling point of the watch is a sensor that can monitor a wearer’s pulse and potentially detect atrial fibrillation.
To test the device’s ability to aid diagnosis, a group of researchers enrolled almost 420,000 Apple Watch wearers in a study. (Some of the researchers were Apple employees, and Apple sponsored the research.) Participants were monitored for about four months. Over that time, 2,161 of the study participants were notified of an irregular pulse, representing just over 0.5 percent of the sample.
Those people were offered telemedicine visits and, if their symptoms were mild, were offered electrocardiogram patches to wear for up to a week to help confirm a diagnosis of atrial fibrillation. Participants mailed the patches back and, if the results indicated an emergency, were contacted immediately and instructed to receive care. If the results were positive for atrial fibrillation but did not require immediate medical attention, the participants were offered a second telemedicine visit and instructed to see their regular physician.
But only 450 of the 2,161 people who were notified about having an irregular pulse returned their sensor patches for evaluation. This means that among those who signed up for the study, wore the watch and got a health alert, almost 80 percent ignored it.
Of the 450 participants who returned patches, atrial fibrillation was confirmed in 34 percent, or 153 people. Those 153 are about 0.04 percent of the 420,000 participants.
This doesn’t mean that the Apple device failed. It probably led some participants to be diagnosed sooner than they might have. How many, and how much of a difference this made in their health, though, is debatable.
Many news outlets reporting on the study mentioned a topline result: a “positive predictive value” of 84 percent. That statistic refers to the chance that someone actually has the condition if he or she gets a positive test result.
But this result wasn’t calculated from any of the numbers above. It specifically refers to the subset of patients who had an irregular pulse notification while wearing their confirmatory patch. That’s a very small minority of participants. Of the 86 who got a notification while wearing a patch, 72 had confirmed evidence of atrial fibrillation. (Dividing 72 by 86 yields 0.84, which is how you get a positive predictive value of 84 percent.)
Positive predictive values, although useful when talking to patients, are not always a good measure of a test’s effectiveness. When you test a device on a group where everyone has a disease, for instance, all positive results are correct.
Other test characteristics like sensitivity (if you have a disease, how likely the test is to be positive) and specificity (if you don’t have a disease, how likely the test is to be negative) are more effective in evaluating the overall quality of a test. This study, unfortunately, was not designed to determine those characteristics.
Other methods to screen and diagnose people with atrial fibrillation are available. A systematic review of mobile health devices for atrial fibrillation found 22 studies between 2014 and 2019 that reported on many of them. Some had sensitivities and specificities pretty close to the ideal of 100. None are close to as large as this study, though.
Even blood pressure monitors, ubiquitous in physician’s offices, can screen for atrial fibrillation. A systematic review of them found that they had sensitivities greater than 85 percent and specificities greater than 90 percent.
Here’s the thing, though. Experts aren’t even sure if screening is a good idea to begin with.
After all, if we felt strongly enough about detecting asymptomatic people who might have atrial fibrillation, we could screen everyone with electrocardiograms. The U.S. Preventive Services Task Force has considered doing this among adults 65 and older, who are at higher risk for stroke. The group found that the evidence was insufficient to recommend doing so, because it’s not clear that this level of screening is better than current care. Just taking a pulse as part of a checkup is a pretty good screen all by itself.
There is also a concern that electrocardiogram screening could turn up a lot of false positives, leading to misdiagnosis and unnecessary further testing, which incurs its own risks. Remember that even with the Apple Watch, most of the people who got notifications did not have atrial fibrillation.
Moreover, the task force was focusing on a population where we might intervene: older people. Patients at high risk of stroke who have atrial fibrillation (i.e., older people) might be treated with anticoagulation. For younger ones at lower risk, it’s not immediately clear how we would treat them, or if we should.
And it’s younger people who are more likely to have a smart watch.
We should be clear that we’re focusing on atrial fibrillation that isn’t otherwise noticed by patients or doctors. Those who are already diagnosed and those who are symptomatic should absolutely be managed by physicians, and many will be treated with medications or procedures. Diagnosed and symptomatic disease should not be minimized or ignored.
There are positive messages from this study. There’s potential to use commercial devices to monitor and assess people outside of the clinical setting, and there’s clearly an appetite for it as well. But for now and based on these results, while there may be reasons to own an Apple Watch, using it as a widespread screen for atrial fibrillation probably isn’t one.
Source: Aaron E. Carroll, The Watch Is Smart, but It Can’t Replace Your Doctor, The New York Times, December 26, 2019.
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Another important factor in considering the usefulness of the collected data is that Apple Watch wearers tend not to be the same population of people concerned about AFib. The former tend to be young, healthy, and affluent, meaning it’s unlikely that consumers will be buying the device strictly for its ECG capabilities, Vox said.
t will take several months of monitoring and a few more incidents of odd heart behavior before I'll get the same sense of confidence I have in my existing routine. But if the first results are anything to go on, Apple has done a fine job with this software.
Apple acknowledged in its FDA submission that the Apple Watch cannot detect AFib when the heart-rate is above 120 beats per minute, and a report today suggests this means it may fail to detect the condition in anywhere between 30% and 60% of cases. Apple has always been careful to stress the limitations of the Watch’s ability to detect AFib. However, it says that the inability of the Watch to detect AFib when the user’s heart-rate is above 120bpm is a very significant limitation.
As Apple announced the new heart health features in their latest Apple Watch, two phrases caught my attention: “Game-changing” and “lifesaving.” One of these phrases may be true (but not as it was intended). And the other should not be used at all – at least not yet.
Now, not for the first time, Apple's attention to user experience has been rewarded: According to a paper outlining the study's design in this week's issue of the American Heart Journal, Apple and Stanford have managed to enroll a staggering 419,093 participants. That makes it the largest screening study on atrial fibrillation ever performed.
Some experts say the Apple Watch's arrhythmia notifications and ECG have enormous potential to benefit public health. But those same experts also express caution and concern. "Apple has essentially gotten out ahead of where medicine is," says Greg Marcus, a cardiac electrophysiologist and the chief of cardiology research at the University of California, San Francisco.
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.
Join an ambitious study to detect the most common heart arrhythmia using your smart watch. Contribute your data and save lives.
The advent of wearable devices that monitor our heart rhythms both excites and worries doctors.
When the new Apple Watch heart monitoring app can get a reading, it can accurately detect that a person has an irregular heart rhythm known as atrial fibrillation 99 percent of the time, according to a study of the new device that Apple submitted to the Food and Drug Administration.
If you're truly concerned about accurate heart rate measurements, you should definitely look into medical-grade options instead of relying solely on a smartwatch.
Aim is to detect the irregular heart rhythms of people living with atrial fibrillation before something life-threatening happens.
Aim is to detect the irregular heart rhythms of people living with atrial fibrillation before something life-threatening happens.
Apple’s new watch can screen for heart problems. But doctors are increasingly worried about the dangers of testing healthy people for disease.
The heart monitor should not be considered a medical device and reflects wider problems with health screens.
Apple Watch’s positive predictive value is just 19.6 percent. That means in this group — which constitutes more than 90 percent of users of wearable devices like the Apple Watch — the app incorrectly diagnoses atrial fibrillation 79.4 percent of the time.
One company is trying to find a way to diagnose severe heart attacks before patients even arrive at the hospital. Preliminary results presented at the 2018 American Heart Association’s Scientific Sessions in Chicago this weekend show that a smartphone app developed by the Silicon Valley-based startup AliveCor may be able to identify heart attacks at home. Specifically, it could detect a type of heart attack caused by complete blockage of an artery—referred to medically as an ST segment elevation myocardial infarction (STEMI)—almost as effectively as an in-hospital electrocardiogram (ECG).
People with atrial fibrillation, which the CDC estimates affects between 2.7 and 6.1 million Americans, could likely benefit from a wearable, on-demand ECG device like the new Apple Watch. (AFib is the most common arrhythmia, and the only kind Apple's watch is approved to detect.) But for everyone else, evidence suggests the potential costs could actually outweigh the proposed benefits. Despite what Benjamin says, there is such a thing as too much insight into one's health.
The additional heart-health functions on the Apple Watch do have the potential to be a step in the right direction. They may well prompt someone with an irregular heartbeat to talk to their physicians about what might be going on, and could stop a more dangerous medical condition before it starts. But it’s possible that the watch flags false-positives—incorrectly stating it’s caught something—causing a user to panic that they have a potentially serious health issue when they do not.
Doctors can also use the monitors to diagnose patients with intermittent episodes of a-fib, which are hard to catch, and follow up on patients who have had ablations, a procedure that removes diseased tissue from the heart to try to stop a-fib symptoms.
Apple has been advertising its watch’s ability to detect atrial fibrillation. The reality doesn’t quite live up to the promise.
Since AFib is only one of the many types of arrhythmias, there is a growing concern among cardiologist that potential costs in terms of false alerts could outweigh the proposed benefits in terms of early detection. However, cardiologists must remember that Afib detection is only the first step for this wearable device. Future algorithmic developments can also cover a majority of arrhythmias including identifying extra beats, supraventricular tachycardias, ventricular arrhythmias, and bradyarrhythmias.
The future of health is on your wrist.