Design of the CHina Epidemiology Research in Subarachnoid Haemorrhage (CHERISH) study.

Rationale: Limited epidemiological data exist on subarachnoid haemorrhage (SAH) in China. Effective prevention requires knowledge of the rates and risk factors for SAH the most lethal type of stroke that most often affects younger adults. We report the methods and the initial experience of a new study to address this deficiency.