Association of Remote History of Venous Thrombosis With Risk of Venous Thrombosis After Age 70 Years.

Importance: Previous venous thrombosis (VT) is associated with risk of future VT, but quantification of risk over the life course is poorly understood. More information is needed for clinicians to understand the association of remote history of VT with the risk of VT in older patients. Objective: To assess the association between a remote history of VT and the development of VT in older age. Design, Setting, and Participants: The Age and Thrombosis, Acquired and Genetic Risk Factors in the Elderly case-control study enrolled patients 70 years and older with VT and control individuals 70 years and older without VT between June 2008 and August 2011. The Age and Thrombosis, Acquired and Genetic Risk Factors in the Elderly study is a 2-center, population-based case-control study that was conducted in Burlington, Vermont, in the US and in Leiden, the Netherlands. Consecutively diagnosed patients with an objectively proven episode of VT (deep vein thrombosis of the leg or pulmonary embolism) were included. Control individuals were identified in the same geographic areas as the patients and were randomly selected. Data were analyzed between May 2021 and October 2021. Exposures: Self-reported remote VT (occurring >10 years before to enrollment). Main Outcomes and Measures: The main outcome was the risk of VT at older age. The association of self-reported history of remote VT with VT at older age was assessed by calculating odds ratios (ORs) as estimates of relative risk with 95% CIs. Results: A total of 460 patients with VT and 456 control participants were included. There were slightly more women than men in both groups (60.2% of patients [n = 277] were women and 52.4% of control participants [n = 239] were women), and the mean (range) age of patients was 78.7 (70.0-100.9) years, which was similar to the control participants. Compared with individuals without remote VT, those with a remote history of VT had an increased risk of VT (OR, 2.54; 95% CI, 1.56-4.13). The crude risk estimate was robust to adjustment and time since remote VT, that is, individuals with a VT 10 to 30 years ago (OR, 2.74; 95% CI, 1.34-5.57) and those with a VT more than 30 years ago (OR, 2.42; 95% CI, 1.21-4.84) had a an increased risk of VT. The population-attributable fraction of a remote history of VT was 7.7%. Conclusions and Relevance: In this study, a remote history of VT was associated with risk of VT in older individuals. This quantification could assist clinicians in advising patients on VT prevention.