Abstract
Background and Purpose: Stroke occurs infrequently in young adults. While a familial basis for older onset stroke is well established, the extent of familial clustering in youngโonset stroke is unknown. To address this issue, we compared the frequency of stroke in relatives of stroke cases to that in relatives of controls across different ages and by stroke subtype. Methods: Through a populationโbased caseโcontrol study of stroke, we identified 487 women aged 15โ49 years with ischemic stroke and 615 women without stroke matched by age and geographic region. Family history of stroke was collected for 5,749 relatives (parents and siblings) of case and control probands by standardized interview. Results: Strokes were reported in 149 relatives of case patients and 119 relatives of controls. Siblings of stroke case patients had more than four times the risk of stroke compared to siblings of controls (OR, 4.17; 95% CI, 1.9โ8.8) and mothers of stroke case patients had twice the risk of stroke compared to mothers of control subjects (OR, 2.02; 95% CI, 1.4โ3.0). The association between stroke in probands and family history of stroke was strongest among women aged 15โ24 years (OR, 2.5; 95% CI, 0.4โ15.1), and diminished with increasing proband age (OR, 1.6; 95% CI, 0.8โ3.3 among women 25โ34 years and OR, 1.5; 95% CI, 1.1โ1.9 among women 35โโ49 years; P<0.0001 for trend). Conclusions: We conclude that youngโonset stroke aggregates in families and that the magnitude of aggregation increases with decreasing proband age. Genet. Epidemiol. 2006. Published 2006 WileyโLiss, Inc.