Sleep disordered breathing and the outcome of stroke.

I nterest in abnormal breathing after stroke has a long history dating back at least to the observations of John Cheyne in 1818. In recent years this interest has been reawakened by a number of publications on the relations between sleep disordered breathing (SDB) and stroke. These studies have been of two main types—those investigating the possible increased risk of stroke in individuals with obstructive sleep apnoea (OSA) and those reporting a high prevalence of SDB after stroke and its possible effects on residual disability and mortality. Unravelling the direction of causality—that is, whether OSA causes stroke or stroke causes OSA—has proved challenging.