Long-term Mortality and Epilepsy in Patients After Brain Abscess: A Nationwide Population-Based Matched Cohort Study

Background. We aimed to determine the long-term risks of mortality and new-onset epilepsy after brain abscess. Methods. Using nationwide population-based medical registries, we examined all patients with first-time brain abscess in Denmark, 1982-2016. Comparison cohorts individually matched on age, sex, and residence were identified, as were siblings of all study participants. Next, we computed cumulative incidences and hazard rate ratios (HRRs) with 95% confidence intervals of mortality and new-onset epilepsy among study populations. Results. We identified 1384 brain abscess patients (37% females) with a median follow-up time of 5.9 years (interquartile range [IQR] 1.1-14.2). The 1-year, 2-5 year, and 6-30 year mortality of patients after brain abscess was 21%, 16%, and 27% as compared to 1%, 6%, and 20% for population controls. Cox regression analyses adjusted for Charlson comorbidity index score showed 1-year, 2-5 year, and 6-30 year HRRs of 17.5 (13.9-22.0), 2.61 (2.16-3.16), and 1.94 (1.62-2.31). The mortality in brain abscess patients was significantly increased regardless of sex or age group except among subjects 80 years or older, and in both previously healthy individuals and immunocompromised persons. Among the 30-day survivors of brain abscess (median follow-up 7.6 years [IQR 2.2-15.5]), new-onset epilepsy occurred in 32% compared to 2% in matched population controls. Cause-specific Cox regression analysis adjusted for stroke, head trauma, alcohol abuse, and cancer showed 1-year, 2-5 year, and 6-30 year HRRs for new-onset epilepsy of 155 (78.8-304), 37.7 (23.0-59.9), and 8.93 (5.62-14.2). Conclusions. Brain abscess is associated with an increased long-term risk of mortality and new-onset epilepsy for several years after infection.