The influence of age and chronic medical conditions on neurological outcomes in out of hospital cardiac arrest.

Abstract

It is unknown whether older patients with out of hospital cardiac arrest (OHCA) have worse outcomes because of aging itself, or because age can be a marker for overall health status. We aimed to study the prognostic utility of age and pre-arrest comorbidities. We conducted a retrospective cohort study, reviewing electronic health records of all adults treated for non-traumatic OHCA in the University of Michigan Emergency Department (N=588). Primary covariates included age, Charlson Comorbidity Index (CCI), and a combined Charlson-age index. The primary dichotomized outcome was favorable neurological outcome (cerebral performance category, 1-2), evaluated by logistic regressions. Dementia (p=0.01), witnessed arrest (p=0.03), bystander CPR (p<0.001), presenting rhythm (p<0.001), and mild therapeutic hypothermia (p<0.001) were associated with the primary outcome. Increasing age (unadjusted OR for each decade of life, 95% CI: 0.78, 0.70-0.88; adjusted 0.79, 0.67-0.94) was negatively associated with likelihood of a favorable neurological outcome. CCI and combined Charlson-age index significantly predicted outcome in the unadjusted, but not adjusted analysis. Composite variables were stronger predictors in patients with shockable than non-shockable presenting rhythms (interaction terms: age and rhythm [p=0.004], CCI and rhythm [p=0.01]). Age, but not CCI, was significantly associated with less favorable neurological outcomes in patients with OHCA after adjusting important covariates. Age appears to be an independent predictor of prognosis rather than a marker for comorbidity.