Johnson & Johnson said on Tuesday it would partner with Apple Inc. on a study to use an iPhone app and the Apple Watch to study how earlier detection of atrial fibrillation impacts stroke in people aged 65 or older.

Last year, Apple's Heart Study found that the watch could accurately detect atrial fibrillation, the most common type of irregular heartbeat, according to a study that explored the role of wearable devices in identifying potential heart problems. Atrial fibrillation increases the risk of stroke more than fivefold, according to the American Heart Association.

Jeff Williams, Apple's chief operating officer, said the initial study proved the Apple Watch can detect atrial fibrillation with a low rate of false alarms, which helped Apple gain clearance from the U.S. Food and Drug Administration for a watch app that takes an electrocardiogram, or EKG, measurement. The study with J&J aims to show if early detection leads to better health outcomes.