Nation-wide retrospective, data-linkage, cohort study of epilepsy and incident dementia.

Schnier, Christian; Duncan, Susan; Wilkinson, Tim; Mbizvo, Gashirai K; Chin, Richard F M

OBJECTIVE To determine the association of epilepsy with incident dementia we conducted a nation-wide retrospective data-linkage, cohort study, to examine whether the association varies according to dementia subtypes and investigate whether risk factors modify the association. METHODS We used linked health data from hospitalisation, mortality records and primary care consultations to follow-up 563,151 Welsh residents from their 60 th birthday to estimate dementia rate and associated risk factors. Dementia, epilepsy and covariates (medication, smoking, comorbidities) were classified using previously validated code lists. We studied rate of dementia and dementia subtypes in people with epilepsy (PWE) and without using (stratified) Kaplan-Meier plots and flexible parametric survival models. RESULTS PWE had a 2.5 (95% CI 2.3 to 2.6) times higher hazard of incident dementia, a 1.6 (95% CI 1.4 to 1.8) times higher hazard of incident Alzheimers disease (AD), and a 3.1 (95% CI 2.8 to 3.4) times higher hazard of incident Vascular dementia (VaD). A history of stroke modified the increased incidence in PWE. PWE who were first diagnosed at age 25 years or younger had a similar dementia rate compared to those diagnosed later in life. PWE who had ever been prescribed sodium valproate compared those who had not, were at higher risk of dementia (HR: 1.6; 99% CI: 1.4 to 1.9) and VaD (HR: 1.7; 99% CI: 1.4 to 2.1), but not AD (HR: 1.2; 99% CI: 0.9 to 1.5). CONCLUSION People with epilepsy, compared to those without epilepsy, have an increased dementia risk.