A study, published in the JAMA, found that middle-aged adults who have a sibling with cardiovascular disease ( CVD ) have a 45 percent increased risk for CVD, a risk that is greater than that conferred by having parents with CVD.

Cardiovascular disease in a first-degree relative confers increased risk for CVD, but whether familial cardiovascular disease is truly an independent risk factor remains controversial.

Risk associated with cardiovascular disease in siblings is uncertain because published estimates are largely derived from case-control studies that generally lack sibling CVD event validation.
Furthermore, estimates regarding magnitude of risk associated with a history of sibling cardiovascular disease vary greatly.

Joanne M. Murabito, of the Framingham Heart Study, and colleagues conducted a study to determine whether the occurrence of a validated sibling CVD event predicted cardiovascular events in a cohort of middle-aged adults, and examined the impact of sibling CVD over and above that of parental CVD.

The researchers analyzed data from the Framingham Offspring Study, a part of the Framingham Heart Study, a population-based study initiated in 1948 with the offspring cohort initiated in 1971. Participants were members of the offspring cohort aged 30 years or older, free of cardiovascular disease, and with at least 1 sibling in the study.
All were followed up for eight years.

Among 973 person-examinations in those who had a sibling with CVD group ( average age, 57 years ) and 4,506 person-examinations in those with no sibling with CVD group ( average age, 47 years ), 329 cardiovascular events occurred during follow-up.

The researchers found that sibling CVD was associated with a 55 percent increased risk for incident cardiovascular disease; this association persisted even after adjustment for risk factors ( 45 percent increased risk ).
The attributable risk percentage for sibling CVD was 27.4 percent; this represents the proportion of the 8-year cardiovascular risk among those in the sibling CVD group that theoretically would not have occurred if members of the group had not had a sibling with cardiovascular disease.

" Using validated events and a prospective design, our study substantially extends the knowledge base regarding the importance of sibling CVD.
We observed that sibling CVD confers increased risks of cardiovascular events above and beyond traditional risk factors and parental premature cardiovascular disease. Thus, sibling CVD should be considered as important as parental premature cardiovascular disease in the assessment of risk.
Further investigation is needed to better understand why sibling history may be a stronger predictor for cardiovascular disease than parental history, including exploration of the contribution of an early shared environment to increased sibling risk. Moreover, investigation of whether to incorporate sibling CVD as well as parental CVD into existing risk prediction and prevention algorithms is warranted," the authors conclude.

Source: American Medical Association, 2005


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