Context: While parental cardiovascular disease (CVD) doubles the risk for CVD in offspring, the extent of increased risk associated with sibling CVD is unclear. Objective: To determine, using validated events, whether sibling CVD predicts outcome in middle-aged adults independent of other risk factors. Design, Setting, and Participants: The Framingham Offspring Study, an inception cohort of the Framingham Heart Study, a prospective population-based cohort study initiated in 1948 with the offspring cohort initiated in 1971. Participants (n = 2475) were members of the offspring cohort aged 30 years or older, free of CVD, and with at least 1 sibling in the study; all were followed up for 8 years. Main Outcome Measures: Association of sibling CVD with 8-year personal risk for CVD using pooled logistic regression. A secondary analysis restricted to offspring with both parents in the study assessed the joint impact of parental and sibling CVD occurrence. Results: Among 973 person-examinations in the sibling CVD group (mean age, 57 years) and 4506 person-examinations in the no sibling CVD group (mean age, 47 years), 329 CVD events occurred during follow-up. Baseline risk factors were more prevalent in the sibling CVD group compared with the no sibling CVD group. Sibling CVD was associated with a significantly increased risk for incident CVD (age- and sex-adjusted odds ratio [OR], 1.55; 95% confidence interval [CI], 1.19-2.03). Adjustment for risk factors did not substantially attenuate the risk (adjusted OR, 1.45; 95% CI, 1.10-1.91). In the analysis restricted to persons with both parents in the study, in models adjusting for both sibling and parental CVD, the multivariable-adjusted OR for sibling CVD (1.99; 95% CI, 1.32-3.00) exceeded that for parental CVD (1.45; 95% CI, 1.02-2.05). Conclusion: Using validated events, sibling CVD conferred increased risk of future CVD events above and beyond established risk factors and parental CVD in middle-aged adults.
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