Risk of venous thrombosis in persons with increased body mass index and interactions with other genetic and acquired risk factors.

UNLABELLED

Essentials Obesity, factor V Leiden (FVL) and blood group non-O are common. We studied the combined effect of these factors on the risk of venous thrombosis (VT). The combination of obesity, non-O blood group and FVL increased VT risk up to ten-fold. Identifying high VT may be beneficial in thrombosis prevention.

SUMMARY

Background Overweight/obesity has a substantial effect on the occurrence of venous thrombosis (VT). Blood group non-O has a high prevalence in Western populations, and the factor V Leiden mutation could be present in 5% of Caucasians. These frequent prothrombotic risk factors will have a considerable impact on the incidence of VT, especially when combined. Objectives We investigated whether FV Leiden with blood group non-O modifies VT risk in individuals with different body mass index (BMI) strata in a case-control study (n = 11253). Results We observed a progressively increasing risk of VT with higher BMI, with an odds ratio of 1.9 (95% confidence interval [CI] 1.6-2.3) for those in the upper BMI tertile (BMI > 26.7 kg m(-2) ), as compared with the first BMI tertile (BMI < 23.5 kg m(-2) , blood group O, and no FV Leiden) (reference group). The addition of FV Leiden and blood group non-O to the model increased the risk in all BMI tertiles; the odds ratios were 3.8 (95% CI 3.2-4.6) in the third BMI tertile of individuals with blood group non-O, and 5.4 (95% CI 3.5-8.5) in the third BMI tertile of individuals with FV Leiden. When both FV Leiden and blood group non-O were present, the odds ratios were 9.1 (95% CI 5.9-14.0) in the first BMI tertile, 9.4 (95% CI 6.6-13.5) in the second BMI tertile, and 12.5 (95% CI 8.9-17.6) in the third BMI tertile. Conclusion Individuals with a high BMI, blood group non-O and/or FV Leiden have a high VT risk. The high VT risks in some subgroups may justify targeted screening and thromboprophylaxis decisions in these patients.