The main goal of this prospective pre-post implementation study is to investigate how a structured testing and treatment program for obstructive sleep apnea using the NOX T3s device and a Fitbit smartwatch with the FibriCheck algorithm impacts the proportion of atrial fibrillation (AF) in an AF population. Participants will wear the NOX T3s respiratory polygraphy device for one night at home. In case of a positive obstructive sleep apnea diagnosis, patients will be referred to the sleep clinic for a polysomnography examination. Patients positively diagnosed with polygraph will be monitored semi-continuously with the Fitbit smartwatch for three months. After the polysomnography examination, the positively diagnosed patients will be monitored semi-continuously for another three months after initiation of treatment (mostly continuous positive airway pressure (CPAP) treatment). Additionally, patients will be administered satisfaction, symptom burden and alcohol consumption questionnaires twice: right after the polysomnography examination and after the 3-month treatment.