ABSTRACT: Essentials Venous thrombosis (VT) risk and coagulation factor levels increase with age. We studied the association between levels of procoagulant factors and the risk of a first VT in the elderly. Higher levels of factors VIII, IX, and XI, but not prothrombin, were associated with the risk of VT. Similar risk patterns were observed for provoked and unprovoked VT and for deep vein thrombosis and pulmonary embolism separately. ABSTRACT: Background Venous thrombosis (VT) incidence increases markedly with age. Coagulation factors are also positively associated with age. Objective To study whether higher levels of coagulation factors II (prothrombin), VIII, IX, and XI are associated with risk of a first VT in the elderly. Methods Four hundred and one patients and 431 control subjects aged 70 and older were included in the Age and Thrombosis, Acquired and Genetic risk factors in the Elderly (AT-AGE) study. Blood was collected 1 year after the event in patients and in all control subjects for measurement of coagulation factors. To assess the risk of VT, odds ratios (ORs) were calculated after stratification of coagulation factors in quartiles and at the 90th percentile, adjusting for potential confounders (age, sex, body mass index, and study center). Results Mean age was 78 years (range: 70-100 years). The ORs of VT for factors in the top quartile compared with the lowest quartile were 4.5 (95% confidence interval [CI]:2.7-7.3) for factor VIII, 2.4 (95% CI:1.1-5.2) for factor IX, and 1.7 (95% CI:1.0-2.9) for factor XI. High prothrombin was not associated with an increased VT risk. There was no dose-response association between the number of high coagulation factors and VT risk. The population attributable risk (PAR) of VT was 37.6%, 23.3%, and 12.4% for factor VIII, IX, and XI, respectively. Conclusion In this study of the elderly, higher factors VIII, IX, and XI but not prothrombin, were positively associated with the risk of VT.
