Abstract P378: Risk Factors for Incident Venous Thrombosis and their Associations with Recurrence
Background: Risk factors for incident venous thrombosis (VT) have been studied extensively, yet less is known about risk factors for recurrent VT in population-based settings. Objective: To evaluate whether established risk factors for incident VT are associated with recurrent VT in women. Methods: In a population-based, case-control study, we identified 1575 incident VT cases in 2002-2010 among women aged 18-89 and 3254 matched controls. Incident VT cases were followed for VT recurrence, defined by physician diagnosis with clinical and/or imaging evidence of a new or expanded clot. We used separate Cox proportional hazards models to evaluate the association of risk factors, assessed at the time of the incident VT, with the hazard of VT recurrence. Established risk factors for incident VT included: age, race, body mass index (BMI), hospitalization or inpatient surgery ≤30 days prior to event, recent cancer diagnosis or treatment, history of cardiovascular disease, and current estrogen use (oral contraceptive or hormone therapy). Incident VT characteristics (distal vs. proximal deep vein thrombosis [DVT] and pulmonary embolism [PE] with or without DVT) were also evaluated. Models were adjusted for all factors simultaneously and were run with and without adjustment for time-dependent oral anticoagulation therapy (OAT). Risk factors were assessed by chart review, telephone interview, and computerized pharmacy records. Results: For these interim analyses, follow-up data were available for 1285 women who were followed for a mean of 39.6 months with a 13% probability of a recurrent VT at 3 years. Higher BMI and recent cancer were associated with an increased risk of recurrent VT. When time-dependent OAT was included in the models, estimates were essentially unchanged. Conclusions: In our population-based study, most risk factors for incident VT were poor predictors of recurrence. However, we provide further evidence that BMI and recent cancers are associated with modestly increased hazards of VT recurrence in women.