If you have a sibling who had a life-threatening blood clot in the legs or pelvis – venous thromboembolism – your risk of suffering the same fate is twice as high compared to other people, researchers from Lund University, Sweden, reported in the journal Circulation. The authors say that theirs is the first study to find a direct link between VTE (venous thromboembolism) and family risk nationwide, sorted by gender and age.

A VTE is a DVT (deep vein thrombosis) in which a blood clot forms in the deep veins, typically in the leg or pelvis. The clot can travel to the lungs and get lodged within the pulmonary arteries – a pulmonary embolism (PE).

Senior study author, Bengt Zöller, M.D., Ph.D., said:

“Hereditary factors – as determined by sibling history – are significant in determining the risk of venous thromboembolism in men and women between the ages of 10 and 69. More importantly, in a fraction of the families we studied, the risk for venous thromboembolism was unusually high – 50 to 60 times higher than those families who were not at risk, thus suggesting a strong genetic risk factor.”

A person whose sibling had VTE has double the risk of developing one themselves, and 50 times the risk of at least two siblings developed the disorder, the authors found.

In this study, the investigators gathered data from the Swedish registries in from 1987 to 2007, this included the Hospital Discharge Register and the Swedish Multigeneration Register. 45,362 hospitalized cases of VTE were identified. Patients ranged in age from 10 to 69, 51.5% were female, and the average age was 50.7 years for males and 46.6 for females. 5.3% (2,393) of them showed a sibling history for the disease.

Below are some more highlighted facts the researchers reported:

  • Males and females aged 10 to 19 years with a sibling history of VTE had a five times higher risk of developing VTE themselves compared to others of their age with no sibling history
  • Males and females aged 60 to 69 years with a sibling history of the disease had double the risk compared to others of the same age
  • The age gap between siblings made no difference to the risk, showing that there was no major familial environmental effect

People whose spouses had VTE had a very slightly higher risk of developing it themselves compared to other people whose spouse never had VTE, indicating that environmental factors did not play a major role in risk, the authors wrote.

VTE affects 1 in every 1,000 people annually, it is the third most common cardiovascular illness, after stroke and heart attack.

Zöller said:

“Our study underscores the potential value of sibling history as a predictor of the risk of venous thromboembolism. Further research is needed to uncover the sources of genetic and non-genetic occurrences of VTE.”

Written by Christian Nordqvist