Nightly Variation in Sleep Apnea Severity as Atrial Fibrillation Risk

Sleep-disordered breathing (SDB) severity is largely determined by the number of apneas and hypopneas/h during a single overnight sleep study, following which patients are categorized as no, mild, moderate, or severe SDB (1). However, SDB severity in an individual patient may not be stable over time, but may instead exhibit a considerable night-to-night variability, which might result in a dynamic exposure to SDB-related conditions affecting the timing and extent of cardiovascular responses such as atrial fibrillation (AF) (2). Although chronic atrial structural alterations have already been described in AF patients with SDB (3), clinical evidence for a dynamic AF substrate related to nightly SDB severity is lacking.