The Apple Heart Study (AHS) is a research study conducted to evaluate whether the Apple Heart Study App can use data collected on the Apple Watch to identify irregular heart rhythms, including those from potentially serious heart conditions such as atrial fibrillation. Up to 500,000 can participate in the study.

Inclusion Criteria:

Possession of the following at time of eligibility screening, ascertained from automatic hardware/software/device pairing check:

• iPhone (5s or later) with iOS version 11.0 or later defined as iPhone model/iOS version used to complete screening eligibility.
• Apple Watch (Series 1 or later) with watchOS version 4.0 or later defined as Apple Watch model/watchOS paired with iPhone used to complete screening eligibility.
• Current resident of the United States at time of eligibility screening, defined by self-reported state of residence within the 50 states of the United States or District of Columbia.
• Proficient in written and spoken English, defined by self-report of comfort reading, writing, and speaking English on iPhone.
• Valid phone number associated with iPhone, ascertained from self-report.
• Valid email address, ascertained from self-report.

Exclusion Criteria:

• Self-reported diagnosis of Atrial Fibrillation.
• Self-reported diagnosis of Atrial Flutter.
• Currently on anti-coagulation therapy.

1 year, 2 months and 14 days (participants may have reported adverse events at any time from enrollment to close of study)