AFib is the leading cause of stroke, but Johnson & Johnson said it can be hard to diagnose because people often don't exhibit symptoms.
In December 2018, Apple began offering AFib detection on the Apple Watch Series 4. A feature allows users to run a quick test using the Apple Watch to see if they may have AFib. Those users can then turn the results into a doctor for further analysis and testing, if needed.
Apple has been laying the groundwork to introduce new health features and studies in its products over the last few years. The company sees health as one of its key areas of growth in the future, hiring dozens of doctors to incorporate more features into its products. Last year, Apple CEO Tim Cook told CNBC's Jim Cramer that he thinks Apple's "greatest contribution to mankind" will be related to health technology.
"The Heartline Study is a nationwide, randomized, controlled, app-based, virtual research study sponsored by Janssen Pharmaceuticals, Inc., a member of the Janssen Pharmaceutical Companies of Johnson & Johnson," the companies said. "The team worked with Apple to jointly design the research study and the Heartline Study app."
Open enrollment for the new study begins Tuesday. It's open to anyone 65 or older with traditional Medicare and an iPhone 6s or later model running iOS 12.2 or newer.
"Eligible participants will be randomized to one of two possible groups. One group will participate by only using the Heartline Study app on their iPhone," Johnson & Johnson explained. "The other group will participate by using the study app on their iPhone in addition to obtaining an Apple Watch to use the ECG app and irregular rhythm notification feature. Participants who already own an Apple Watch may be eligible to join the study as well, with certain restrictions."
Participants selected in the Apple Watch group can either purchase a watch at a discounted price or can borrow a watch on loan for no cost. Those who borrow will have to return the watch at the end of the study. The exact discounted price wasn't disclosed.
The app is available for free in the iTunes App Store.
Heartline will last three years and includes two years of active engagement and one year of additional data collection, Johnson & Johnson said.
Apple and Stanford published the results of an earlier heart study in November. It was the largest of its kind and was covered in The New England Journal of Medicine. That research included 419,000 participants over 8 months and found that just over 2,000 people received a notification of an irregular pulse. But results of that were debated and many agreed that they were still preliminary.
Correction: This story has been updated to reflect you do not need an Apple Watch to participate in the study.