Increased risks of tic disorders in children with epilepsy: A nation-wide population-based case-control study in Taiwan.

Both epilepsy and tic disorders may share common mechanisms with the involvement of abnormal cortical-basal ganglion circuit connection and dopaminergic dysfunction. However, the association between epilepsy and tic disorders has never been studied. This study investigated the risks of developing tic disorders among children with epilepsy using databases of a universal health insurance system in Taiwan. The data analyzed in this study were retrieved from the National Health Insurance Research Database in Taiwan. The study cohort included children with epilepsy between 2001 and 2007 (n=2629) and a three-fold age- and gender-matched controls (n=7887). All subjects were followed up for 3 years from the date of cohort entry to identify their admissions due to tic disorders (ICD-9-CM codes 307.2, 307.20-307.23). Cox hazard regression analysis was performed to estimate the effect of epilepsy on the occurrence of tics. The epilepsy cohort had a higher prevalence of tics (1.7% vs. 0.2%), and a 8.70-fold increased risk of developing a tic disorder compared with the controls (adjusted hazard ratio (AHR) 8.70, 95% confidence interval (CI) 4.26-16.37, p<0.001). Male patients were observed to have a higher risk of developing a tic disorder (AHR 1.90, 95% CI=1.04-3.46, p<0.001) compared to female individuals. Patients with multiple antiepileptic drugs treatment also exhibited higher crude OR for developing tic disorders. This nationwide population-based cohort study, for the first time, demonstrated that there is a significantly increased risk for tic disorders among children with epilepsy. We also found males, attention deficit disorder and the use of multiple AEDs to be independent risk factors of tic disorders. Closely evaluating possible tic disorders would be crucial for improving the outcome and life quality in children with epilepsy.