Elevated factor VIII increases the risk of cerebral venous thrombosis: a case–control study

Background: Elevated factor VIII (FVIII) is a risk factor for leg-vein thrombosis and pulmonary embolism. We assessed whether elevated FVIII is also a risk factor for cerebral venous thrombosis (CVT). Methods: We performed a matched case–control study. We assessed patients with CVT, as cases, admitted between July 2006 and December 2016. The controls were healthy hospital-staff employees matched for age (within 5 years) and sex. FVIII activity was measured at least 3 months after CVT diagnosis. Elevated FVIII was defined as activity > 150 IU/dl. We used logistic regression analysis, adjusting for age and sex. Results: We included 116 cases and 116 controls (85% women for both groups). Mean age was 40 (SD 11) and 41 (SD 11) years for cases and controls, respectively. Median time between CVT diagnosis and blood collection was 18 months (IQR 7–39 months). Cases more often had elevated FVIII as compared to controls (83.6 vs 28.4%, p < 0.001). After adjustment, elevated FVIII was associated with a 15-fold increased risk of CVT (OR 15.3, 95% CI 7.8–30.1). Stratification by sex showed a stronger association in men (OR 22.8, 95% CI 2.8–184.3) than in women (OR 14.7, 95% CI 7.2–30.2). Conclusion: Elevated FVIII occurs frequently in patients with CVT and is a strong risk factor for this condition.