Hospitalizations and deaths were ascertained via annual follow-up phone calls, study examinations, and surveillance of hospital discharges in ARIC communities. Hospitalizations meeting one or more of the following criteria were eligible for medical record abstraction: 1) A discharge diagnosis ICD-9-CM code 430 through 438 (1987–1996) or 430 through 436 (since 1997); 2) One or more stroke-related keywords (see Supplemental Methods) in discharge summary; or 3) Diagnostic computed tomography (CT) or magnetic resonance imaging (MRI) scan with cerebrovascular findings or admission to the neurological intensive care unit. A trained nurse abstracted records for each eligible hospitalization, including up to 21 ICD-9-CM discharge codes (see Supplemental Methods).
A computer algorithm and physician reviewer independently classified each event according to criteria adapted from the National Survey of Stroke.22 (link) A second physician reviewer adjudicated in cases where the computer and initial reviewer disagreed.
A definite or probable stroke was defined as a sudden and rapid onset of neurological symptoms lasting >24 hours or leading to death in the absence of evidence for a non-stroke cause (see Supplemental Material). Events that did not meet these criteria were classified as “possible stroke of undetermined type,” “out-of-hospital fatal stroke,” or “no stroke.” Definite and probable strokes were classified further as SAH, ICH, or ischemic stroke (including embolic and thrombotic brain infarction) (Supplemental Table I).23 (link)