Risk of venous thromboembolism in people with epilepsy.

Objective: Risk of venous thromboembolism (VTE) among people with epilepsy (PWEs) has not been previously reported. Standard VTE prevention methods may increase the risk of complications in this population. This statewide study assessed the risk of VTE in PWEs.

Methods: Main risk categories were grouped into definite epilepsy (DE), probable epilepsy (PE), and migraine, a comparable neurologic condition. All inpatient, emergency department, and hospital-based outpatient encounters in South Carolina from January 1, 2000 through December 31, 2011, were evaluated for the primary outcome variable of VTE, defined as having a diagnosis of VTE at or after the diagnosis of epilepsy or migraine. Coagulopathies and common comorbidities of epilepsy were enumerated. Differences in VTE proportions were assessed using 95% confidence intervals (CIs). Association of VTE with epilepsy and migraine was evaluated with Cox proportional hazard modeling.

Results: A total of 138,497 people with migraine (PWMs) and 67,900 PWEs (32,186 DE, 35,714 PE) were included. VTE occurred in 2.7% of PWEs (4.2% among DE), and 0.6% of PWMs. The hazard ratio for VTE in DE compared with PWMs was 3.08 (95% CI 2.76-3.42), adjusted for all covariables. Higher numbers of comorbidities were strongly associated with VTE. PWE had higher numbers of comorbidities (52% with 2+ comorbidities versus 23% of PWM), but the impact of comorbidities on VTE risk was larger in PWM.

Significance: Higher VTE risk in PWE than PWM suggests risk factors associated with epilepsy, independent of chronic neurologic illness. VTE occurrence in PWE is comparable to published rates among people with cancer.