Objective: Dementia and epilepsy often co-occur and are associated with poor health outcomes and increased healthcare utilization. The literature on the association between readmission and co-occurrence of dementia and epilepsy is scant. Our objective was to determine if dementia in patients with epilepsy >40 years old is associated with 30-day hospital readmission, in-hospital mortality, discharge disposition, and length-of-stay. Methods: This retrospective cohort study used the 2014 Nationwide Readmissions Database, containing data from hospital discharges across the US and readmissions. Epilepsy and dementia were identified using previously validated ICD-9-CM codes. Primary outcome was 30-day readmission, analyzed with univariable and multivariable logistic regressions. Secondary outcomes were discharge disposition, in-hospital mortality, and length-of-stay, analyzed with univariable multinomial logistic, univariable logis-tic, and univariable ordinary least squared regressions, respectively. The top ten causes of readmission in each group were compared as well. All analyses accounted for survey weights, cluster, and stratum. Results: Patients with epilepsy with dementia (n =15,588) had longer hospital stays [15% (95%CI 10- 20%)], and higher odds of readmission [OR 1.11 (95%CI 1.05-1.17)], transfer to another facility [OR 2.18 (95%CI 1.93-2.46)], and in-hospital mortality [OR 1.50 (95%CI 1.25-1.79)] compared to those with-out dementia (n = 186,289). The top two causes of readmission were septicemia (dementia: 14.81%; no dementia: 9.45%) and epilepsy/convulsions (dementia: 5.91%; no dementia: 6.25%). Other top 10 causes of readmissions in those with epilepsy and dementia which were not present in those without dementia included delirium (5.21%), urinary tract infections (4.98%), and aspiration pneumonitis (4.29%). Significance: Dementia in epilepsy is associated with worse outcomes, including higher in-hospital mor-tality and higher readmissions. Potentially preventable causes of readmission in those with epilepsy and dementia were identified, including septicemia, delirium, urinary tract infection, and aspiration pneu-monitis. Future studies are needed to inform interventions aimed at decreasing premature mortality and reducing potentially preventable readmissions in this vulnerable population. (c) 2021 Elsevier Inc. All rights reserved.