Age May Modify the Relationship between Factor V Leiden Mutation - but Not G20210A Prothrombin Gene Variation - and Idiopathic Venous Thromboembolism: An Hospital-Based Case-Control Study.

Abstract

Introduction:Factor V Leiden is the most common inherited risk factor for venous thromboembolism (VTE). A four- to sevenfold increased risk of VTE for the heterozygous state has been reported by numerous epidemiological studies but most of them did not include patients over 70 years. Surprisingly, we found in a previous study no association between Factor V Leiden and VTE in patients over 70 years.MethodsTherefore we conducted a large hospital-based matched case-control study to test the hypothesis of an interaction between age and the factor V mutation, as well as G20210A prothrombin gene variation.Results:We analysed 392 patients experiencing VTE not related to a major acquired risk factor and their matched controls. Factor V Leiden was not associated with VTE in patients aged 80 years and over: odds ratio 0.8 (95%CI 0.2-3.4). There was a significant interaction between age and the mutation for VTE risk (p=0.03). Conversely, the association between the G20210A variant and VTE was consistent across age-groups: odds ratio 2.8 (95%CI 1.4–5.8).In conclusion, age may modify the relation between factor V Leiden and VTE. The prevalence of the factor V mutation decreased with increasing age among patients with VTE but not among controls.