The Apple Heart Study participants were people without atrial fibrillation who purchased a smart phone app and consented to monitoring using a smartwatch-based irregular pulse notification algorithm, which identified possible atrial fibrillation. If notification occurred, the person was mailed an electrocardiography (ECG) patch to be worn for seven days to confirm the findings first identified by the smartwatch. The age distribution of this group is different than the usual cohort at risk for atrial fibrillation: 52% were between the ages of 22 and 39 years of age, and only 5.9% were 65 years or older. A much more useful study would have included an older cohort that carries a higher risk of atrial fibrillation.