History of blood clots doubles risk for family members

Children and siblings of those with blood clots appear to have double the risk of developing the condition, scientists claim.

A report published in the Archives of Internal Medicine details how researchers collected blood samples, along with information about family history and environmental risk factors from patients who had experienced their first clot between 1999 and 2004.

Their data was compared with control participants who were the same sex and age, but had not had venous thrombosis.

The study found among those with venous thrombosis, 31.5 per cent had at least one first-degree relative with a history of the condition, compared with 17.3 per cent in the other group.

A positive family history was associated with a more than two-fold increase in the risk of venous thrombosis. The danger was increased further if the relative developed clots at a younger age and as much as quadrupled if more than one relative was affected.

The authors claim the results may indicate unknown genetic risk factors or that venous thrombosis may cluster in a family due to characteristics of the shared household.