Background and Purpose--Family history of stroke (FHx_stroke) is a risk factor for ischemic stroke, but there are insufficient data on the relationship with stroke subtypes and intermediate phenotypes (IPs), such as hypertension. Specifically, there are no reliable data on the associations of FHx_stroke in patients with transient ischemic attack (TIA) in whom relationships with IPs are likely to be determined most reliably.

Methods--We studied FHx_stroke and FHx of myocardial infarction (FHx_MI) in TIA patients from 2 population-based incidence studies and 2 prospective consecutive hospital-referred series. We related the presence of FHx to baseline characteristics, clinical subtype, and IPs.

Results--Results were similar in the 4 cohorts, and so data on all 783 patients were pooled. FHx_stroke was less common than FHx_MI (189 versus 254; P=0.0003). FHx_stroke and FHx_MI were strongly related to history of hypertension in the proband (odds ratio [OR], 1.78; 95% CI, 1.28 to 2.48; P=0.0008; and OR, 2.10, 95% CI, 1.55 to 2.85; P<0.0001, respectively). Highest recorded premorbid systolic and diastolic blood pressures (mm Hg) were significantly higher in cases with FHx_stroke than those without and increased with the number of affected first-degree relatives (0 181/100; 1 185/104; 2 198/109; P=0.03). There was no association between FHx_stroke and age, diabetes, smoking, plasma glucose, cholesterol, or territory of TIA, but FHx_stroke was less common in patients with ocular TIA than in cases with cerebral TIA (OR, 0.53; 95% CI, 0.34 to 0.82; P=0.004), although the association was no longer significant after adjustment for hypertension.

Conclusions--The strong association between hypertension and FHx_stroke suggests that familial susceptibility to cerebral ischemia is attributable, at least partly, to familial predisposition to hypertension. This should be taken into account in studies of the genetics of ischemic stroke.