Clinical Epidemiology, Risk Factors, and Outcomes of Encephalitis in Older Adults

Abstract

Background: Encephalitis is associated with significant morbidity and mortality, with unknown etiologies in the majority of patients. Large prognostic studies evaluating elderly patients are currently lacking.

Methods: We performed a retrospective cohort of encephalitis cases in 19 hospitals from New Orleans, Louisiana, and Houston, Texas, between the years 2000 and 2017.

Results: A total of 340 adult (aged ≥17 years) patients with confirmed encephalitis were enrolled, and 194 (57%) had unknown etiologies. A cerebrospinal fluid polymerase chain reaction (PCR) for herpes simplex virus (HSV) and varicella zoster virus was done in 237 (69%) and 82 (24%) patients, respectively. Furthermore, an arboviral serology was done in 169 (49%) patients and measurements of anti-N-methyl-D-aspartate receptor antibodies were taken in 49 (14%) patients. A total of 172 out of 323 patients (53%) had adverse clinical outcomes (ACOs) at discharge. Older individuals (>65 years of age) had a lower prevalence of human immunodeficiency virus, had a higher number of comorbidities, were less likely to receive adjuvant steroids, were more likely to have a positive arbovirus serology, were more likely to have a positive HSV PCR, were more likely to have abnormal computerized tomography findings, and were more likely to have to have an ACO (all P values < .05). Prognostic factors independently associated with an ACO were age ≥65, fever, Glasgow Coma Scale (GCS) score <13, and seizures (all P values ≤0.01).

Conclusions: Encephalitis in adults remain with unknown etiologies and adverse clinical outcomes in the majority of patients. Independent prognostic factors include age ≥65 years, fever, GCS score <13, and seizures.

Keywords: encephalitis; older adults; outcomes; prognosis; risk factors.