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An unprecedented study suggests the Apple Watch can help detect heart problems. But very few people actually used it to do that. (AAPL)

Hollis Johnson

  • At the beginning of the year, Apple CEO Tim Cook said his company's "greatest contribution to mankind" would be in health.
  • So, can the Apple Watch help spot heart problems? A study published Wednesday says yes.
  • There are caveats.
  • The study did not use the most recent Apple Watch, which has a special sensor designed to detect heart issues. Instead, it used previous versions of the Watch, which use lights.
  • In addition, few people recruited for the research actually completed it. 

Apple CEO Tim Cook started 2019 with a bang.

"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," he told CNBC in a January interview.

A study published on Wednesday in The New England Journal of Medicine provides a look at how that vision might take shape. Called the Apple Heart Study, the research was designed to see whether the Apple Watch and its heart-rate sensor could properly spot irregularities in people's heartbeat. One key abnormality is a condition called atrial fibrillation, or afib.

Overall, the research suggests that the Apple Watch does a fairly good job of detecting afib. Notably, the study did not use the most recent Apple Watch, which has a special sensor designed to detect heart issues. Instead, it used previous versions of the Watch, which use lights.

In some cases, the devices also spot problems when there aren't any, something that could send healthy people flocking to healthcare providers for care they don't need. In other cases, Apple Watches failed to spot problems. That could lead some people with afib to falsely believe they don't have the condition.

People with afib often deal with shortness of breath and poor blood flow. The condition can also increase the risk of more serious problems like stroke and heart failure.

Importantly, very few of the study participants who were flagged as potentially having afib actually ended up completing the study. A lot of them simply dropped out.

"I think the most surprising or interesting finding is the drop-out rate," Mohamed Elshazly, an assistant professor of medicine at Weill Cornell Medical College who reviewed the study's design and saw its preliminary results, told Business Insider. 

"This should make us rethink how to do these kinds of studies in the future," Elshazly added.

An example for tech giants with their eyes on health?

Apple isn't the only Silicon Valley tech giant with its eye on health. In recent years, companies such as Facebook, Google parent company Alphabet, and Fitbit (which Google recently agreed to acquire) have all made an effort to detect and prevent illness — whether it's picking up on someone who might be at risk of suicide or diagnosing a condition like afib or sleep apnea.

Ailments like afib may be a kind of holy grail for these companies because they are equal parts common, serious, and preventable.

"The study's findings will help patients and clinicians understand how devices like Apple Watch can play a role in identifying atrial fibrillation," Mintu Turakhia, the study's lead author and an associate professor of cardiovascular medicine at Stanford, said in a November statement.

Apple did some things really well with this study, Elshazly said.

As examples, he cited the fact that the research was done in collaboration with Stanford; included lots of people; and took place over a fairly long time period. Additionally, the study design was kept separate from Apple, who funded it.

Another strength is that the Apple Watch appears to be highly selective: it only flagged a very small slice of the overall population as having potential heart issues, Elshazly said. Out of more than 400,000 people recruited for the study, only 0.5% — or about 2,000 people — were notified that they might have an irregular heart rate. 

The Watch appears to be good at spotting problems where there really are problems, Elshazly said. Out of the people who got Apple Watch alerts, 84% had afib and were having an episode at the time of the notification. 

But there were weaknesses too, said Elshazly.

The study raises new questions about digital health efforts

Roughly 79% of people who got an initial notice that they might have afib didn't complete the study or were later excluded from it. Most of them dropped out, or failed to do one of the remote visits that the study required.

"That's a huge number," Elshazly said. "Most clinical trials wouldn't continue with a drop-out figure that high."

Also, some people who actually have afib were missed by the Watch. According to the paper, at least 3,000 people who were later diagnosed with afib did not receive a notification from Apple. Elshazly thinks this could be a bigger problem than the study lets on.

"There will be a large percentage of people wearing the Apple Watch thinking they are accurately monitored and safe from afib," when in reality they have the condition, Elshazly said. 

Larry Husten, the former editor of TheHeart.Org, previously agreed with Elshazly on this.

In an opinion piece for Stat News from this March, he wrote, "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."

Unfortunately, the researchers in Apple's latest study didn't monitor people whose Watches didn't spot an irregularity, so we have don't know how many of these "falsely reassured" people there might be, Elshazly said.

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