To cite this article: Engbers MJ, Blom JW, Cushman M, Rosendaal FR, van Hylckama Vlieg A. The contribution of immobility risk factors to the incidence of venous thrombosis in an older population. J Thromb Haemost 2014; 12: 290-6. Summary. Background: Venous thrombosis is common in the older population. Assessment of risk factors is necessary to implement preventive measures. Objectives: We studied the associations between immobility-related risk factors and thrombosis, specifically, hospitalization, surgery, fractures, plaster cast use, minor injuries, and transient immobility at home, in an older population. Patients and Methods: Analyses were performed in the Age and Thrombosis, Acquired and Genetic risk factors in the Elderly (AT-AGE) study, a two-center population-based case-control study. Consecutive cases aged > 70 years with a first-time thrombosis (n = 401) and control subjects > 70 years old without a history of thrombosis (n = 431) were included. Exclusion criteria were active malignancy and severe cognitive disorders. We calculated odds ratios (OR) with 95% confidence intervals (95% CI) after adjustment for age, sex, body mass index, study center, and population-attributable risks. Results: There was a 15-fold (OR 14.8, 95% CI 4.4-50.4) increased risk of thrombosis within 2 weeks after hospital discharge. Surgery (OR 6.6, 95% CI 3.7-11.6), fractures (OR 12.7, 95% CI 3.7-43.7), plaster cast (OR 6.2, 95% CI 2.0-18.9), minor leg injuries (OR 1.9, 95% CI 1.1-3.3), and transient immobility at home (OR 5.0, 95% CI 2.3-11.2) were all associated with thrombosis risk over 3 months. The population-attributable risks for in-hospital immobility was 27%, and for out-of-hospital immobility, 15%. Conclusions: In those > 70 years of age, in-hospital and outof hospital immobility are strong risk factors for thrombosis. Additional studies on preventive measures during immobilization in this age group should not focus solely on hospital settings.
