Apple has launched an app to collect data from Apple Watch users in order to detect and notify them when they experience irregular heart rhythms, like atrial fibrillation -- a leading cause of strokes.

The app, called "Apple Heart Study", will be using Apple Watch's heart rate sensor. Apple said it is collaborating with Stanford University to improve the technology which is used to detect and analyse irregular heart rhythms. "Working alongside the medical community, not only can we inform people of certain health conditions, we also hope to advance discoveries in heart science," said Jeff Williams, Apple's Chief Operating Officer. The Apple Heart Study app is available in the US App Store to customers who are 22 years or older and have an Apple Watch Series 1 or later, Apple said in a statement on Thursday. To calculate heart rate and rhythm, Apple Watch's sensor uses green LED lights flashing hundreds of times per second and light-sensitive photodiodes to detect the amount of blood flowing through the wrist. 

The sensor's optical design gathers signals from four distinct points on the wrist, and when combined with powerful software algorithms, Apple Watch isolates heart rhythms from other noise. The Apple Heart Study app uses this technology to identify an irregular heart rhythm. As part of the study, if an irregular heart rhythm is identified, participants will receive a notification on their Apple Watch and iPhone, a free consultation with a study doctor and an electrocardiogram (ECG) patch for additional monitoring, Apple said. "We're excited to work with Apple on this breakthrough heart study," said Lloyd Minor, Dean of Stanford University School of Medicine.