Background and Purpose--The magnitude of inherited risk of stroke may lessen with age, and this would have implications for optimizing genomic approaches to identifying genetic risk factors for stroke. We investigated the relationship between age and inherited risk of stroke.

Methods--Family histories of stroke were obtained in systematic interviews with 310 adult men and women with recent CT- or MR-confirmed ischemic stroke. Probability of stroke in first-degree relatives was analyzed by logistic regression, adjusting for sibship size.

Results--The probability of having a sibling with stroke increased as proband age at stroke presentation increased. Per decade increase in proband age, the odds ratio was 1.65 (95% confidence interval [CI], 1.20 to 2.28; P=0.002) for a concordant sibling and 1.69 (95% CI, 1.15 to 2.49; P=0.008) for 2 first-degree relatives with a history of stroke.

Conclusions--Clustering of stroke was not greater in families with probands manifesting symptoms of stroke in earlier than later adulthood. The relationship between proband age and positive family history of stroke does not suggest an upper age-limit cutoff for genomewide linkage studies.