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

Aim: 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.

Methods: 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.

Results: 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]).

Conclusion: 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.