Family history of stroke does not predict risk of stroke after transient ischemic attack

Background and Purpose - Animal models suggest a genetic contribution to cerebral susceptibility to ischemia. Family history of stroke (FHx(stroke)) is a risk factor for ischemic stroke, but there is significant confounding by heritability of hypertension and other intermediate phenotypes, and it is uncertain whether genetic factors have a direct independent influence on cerebral susceptibility to ischemia in man. Methods - We related detailed FHx(stroke) to baseline characteristics and subsequent risk of stroke in 2 population-based incidence studies and a consecutive hospital-referred series of patients with recent transient ischemic attack (TIA). Results - In none of the cohorts or the pooled data (757 patients; 5515 patient years follow-up; 200 ischemic strokes; 126 myocardial infarctions [MIs]) did FHx(stroke) predict ischemic stroke (odds ratio [OR], 0.87; 95% CI, 0.57 to 1.32). No associations were revealed by analyses stratified by age or hypertension in the proband, FHx(stroke) in parents versus siblings, number of affected relatives, or their age at stroke. FHx(stroke) was unrelated to presence of ischemic lesions on baseline computed tomography (OR, 0.96; 0.52 to 1.76) or risk of MI during follow-up. There was no bias attributable to any relationship between FHx(stroke) and risk factor control or medication. Conclusions - Family history of stroke does not predict risk of ischemic stroke after TIA.