OBJECTIVE: The aim of this study was to quantify daytime symptoms in atrial fibrillation (AF) patients with and without sleep related breathing disorders (SRBD). BACKGROUND: SRBD are common in patients with AF but little is known about daytime symptoms among those with SRBD. METHODS: Patients with AF admitted to clinics of two tertiary referral hospitals for a variety of different cardiovascular diseases were screened with a trans-nasal airflow measurement device allowing measurement of the apnea-hypopnea-index. Data on cardiac risk factors, left ventricular ejection fraction (LVEF) and cardiac medication were collected. Presence of SRBD was defined as an AHI ≥ 15/h. The Epworth sleepiness scale (ESS) was used to quantify daytime symptoms. RESULTS: Of 102 screened patients 8 were excluded due to device malfunction (n=1), dislocation of nasal cannula (n=6), or hyperthyroidism (n=1). Among the remaining 94 patients, 40 (43%) were diagnosed with SRBD. Patients with and without SRBD had similar age, body mass index, LVEF and cardiac medication. The prevalence of coronary artery disease was higher in patients with SRBD than in those without (50 vs. 17%; p=0.0007). ESS score was low and similar in both groups (no SRBD: median 4, interquartile range (IQR) 2-4 vs. SRBD: 5, IQR 3-8; p=0.14). Only 6/40 (5%) of the patients underwent overnight polysomnography and 2 (5%) started CPAP ventilation during follow-up. CONCLUSIONS: Even though SRBD are common in patients with AF, the prevalence of daytime symptoms is rare. Consequently, most patients will not initiate CPAP ventilation after positive SRBD screening. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.