Risk of blood clots in veins: Hereditary factors studied in Swedish study

"Previously, hereditary factors for venous thromboembolism have only been studied on a small scale. We based our study on the entire Swedish population," says Bengt Zöller, researcher at the Centre for Primary Health Care Research, Malmö. Using the national multi-generation register and hospital discharge register, the researchers examined the risk of being affected if one or both parents have had venous thromboembolism. During the period 1987 to 2007, a total of 45 362 people suffered from venous thromboembolism, of whom 4 865 had hereditary VTE and thus a higher risk of being affected.

The study shows that hereditary factors are of most significance at a younger age -- between 10 and 50 -- and occur in both men and women. The highest relative risk was seen in the 10-19 age group. After the age of 50, other factors appear to play a greater role than hereditariness. Blood clots in the very young, under the age of 10, are rare, but strangely enough, hereditary factors do not appear to be the most significant in this age group. The highest risk occurs if both parents have had venous thromboembolism.

"The findings are an important guide to the importance of hereditary factors for VTE. In conclusion, a parental history of venous thromboembolism is an important risk factor that should be included in the clinical medical history and examination," says Bengt Zöller.