AGE-SPECIFIC INCIDENCE RATES OF VENOUS THROMBOEMBOLISM AMONG HETEROZYGOUS CARRIERS OF FACTOR-V LEIDEN MUTATION

Background: Previous reports suggest that younger carriers of the fact or V Leiden mutation are at greater risk for venous thromboembolism th an are older carriers. However, available data on thromboembolic risk are limited. Objective: To determine age-specific incidence rates of v enous thromboembolism associated with the factor V Leiden mutation. De sign: Prospective cohort study. Patients: 14 916 initially healthy men participating in the Physicians' Health Study who were followed from 1982 to August 1994 for the occurrence of deep venous thrombosis or pu lmonary embolism. Measurements: Polymerase chain reaction was used to determine factor V Leiden mutation status in 156 study participants wh o developed venous thromboembolism during follow-up and in 2406 study participants who remained free of vascular disease. Results: Risks for venous thromboembolism in heterozygous carriers of factor V Leiden mu tation increased with age at a rate significantly greater than that in noncarriers. Whereas incidence rates of venous thromboembolism were s imilar in men with and men without the factor V Leiden mutation who we re younger than 50 years of age, incidence rate differences (per 1000 person-years of observation) between affected and unaffected men incre ased significantly from 1.23 (95% CI, -0.4 to 2.9) for those aged 50 t o 59 years to 1.61 (CI, -0.5 to 3.7) for those aged 60 to 69 years of age to 5.97 (CI, 0.6 to 11.3) for those aged 70 years or older (P for trend = 0.008). For idiopathic venous thromboembolism, age-specific in cidence rate differences between men with and without the factor V Lei den mutation increased significantly with age (P = 0.017). However, no significant relation was found for secondary events (P > 0.2). Conclu sions: The findings support the hypothesis that the pathogenesis of ve nous thromboembolism involves acquired as well as genetic risk factors and indicate that determination of factor V Leiden mutation status sh ould not be limited to young patients.