Parkinson disease and the risk of epileptic seizures

Objective To assess the association between incident Parkinson disease (PD) and subsequent incident epileptic seizures. Methods We conducted a retrospective cohort study with a nested case–control analysis using data from the U.K. Clinical Practice Research Datalink. We identified patients aged ≥40 years with an incident diagnosis of PD between 1995 and 2016 and a matched comparison group of PD‐free individuals. We calculated crude incidence rates (IRs) with 95% confidence intervals (CIs) of epileptic seizures in PD patients and the PD‐free comparison group, and corresponding crude incidence rate ratios (IRRs). In the nested case–control analysis, we calculated adjusted odds ratios (adj. ORs) of incident PD among cases with incident epileptic seizures and seizure‐free controls overall and stratified by various seizure‐provoking comorbidities. Results Among 23,086 incident PD patients and 92,343 PD‐free individuals, we identified 898 patients with incident epileptic seizures. The crude IR of epileptic seizures in PD patients was 266.7/100,000 person‐years (95% CI = 235.6–297.7), and in PD‐free individuals it was 112.4/100,000 person‐years (95% CI = 103.5–121.3; IRR = 2.37, 95% CI = 2.06–2.73). The adj. OR of epileptic seizures was 1.68 (95% CI = 1.43–1.98) in PD patients compared with PD‐free individuals. PD patients with comorbid brain disorders (adj. OR = 12.36, 95% CI = 8.74–17.48) or with > 1 seizure‐provoking comorbidity (adj. OR = 13.24, 95% CI = 10.15‐17.25) were at the highest risk of epileptic seizures compared with PD‐free individuals with no seizure‐provoking comorbidities. Interpretation This study suggests that incident PD is associated with an increased risk of incident epileptic seizures. Ann Neurol 2018;83:363–374