The goal of this clinical trial is to find out if testing for sleep apnea (a condition where breathing stops and starts during sleep) at home can improve well-being in people with atrial fibrillation (an irregular heartbeat condition). About 936 participants will be involved. They will either be tested for sleep apnea and treated, if needed, or not tested at all. Researchers will compare the well-being and heart-related symptoms of participants who are tested for sleep apnea to those who are not. These will be tracked using a mobile app to monitor symptoms, physical activity, and heart rhythm. Main hypothesis: Participants with atrial fibrillation who are tested and possibly treated for sleep apnea will have improved quality of life scores (measured by the Atrial Fibrillation Effect on QualiTy-of-life (AFEQT) questionnaire) by at least 5 points after 18 weeks.