Risk factors for venous thromboembolism in the elderly: results of the master registry

Approximately 50-75% of patients with venous thromboembolism have a readily identifiable risk factor, either transient or permanent, whereas the remaining episodes are classified as unprovoked. The incidence of first-time venous thromboembolism rises exponentially with age. Whether the prevalence and the relative weight of major risk factors differ between elderly and younger patients is unclear. We performed a multicenter, prospective, observational study on consecutive patients with objectively confirmed acute venous thromboembolism admitted to 25 Italian hospitals. Baseline characteristics and information on temporary and permanent risk factors at the time of the index event were secured by an electronic data network. We enrolled 2119 patients (49.8% men), of whom 440 (20%) were more than 75 years of age and 1679 (79.2%) 75 years of age or less. Elderly patients were more likely to have pulmonary embolism at presentation (33.6 and 25.6%, respectively, P < 0.001). After binary logistic regression analysis, we found that the risk of venous thromboembolism in the elderly, compared with the younger age group, was significantly associated with immobilization (odds ratio: 2.46, 95% confidence interval: 1.85-3.27) and with severe medical disorders (odds ratio: 1.99, 95% confidence interval: 1.41-2.80), whereas male sex (odds ratio: 0.53, 95% confidence interval: 0.42-0.66), surgery (odds ratio: 0.61, 95% confidence interval: 0.43-0.85), and trauma (odds ratio: 0.49, 95% confidence interval: 0.31-0.77) were less common risk factors in the elderly than in younger patients. Use of thromboprophylaxis prior to the index event was not different between the two age groups. Severe medical disorders and immobilization are strongly associated with the occurrence of venous thromboembolism in the elderly. Our findings stress the need for adequate thromboprophylaxis in this setting.