The influence of comorbidity on survival and long-term outcomes after out-of-hospital cardiac arrest

Introduction Comorbid conditions have been associated with morbidity, functional status and quality of life for patients with a wide range of diseases. Previous studies have attempted to elucidate the influence of pre-arrest comorbidities on survival and neurological recovery following out-of-hospital cardiac arrest (OHCA), however the findings are conflicting. Methods Baseline comorbidities recorded within prehospital patient care records were linked with baseline and 12-month follow-up data from the Victorian Ambulance Cardiac Arrest Registry for adult (≥16 years) non-traumatic OHCA patients. Dates of death from the Victorian death registry were also obtained for patients surviving to hospital discharge. Multivariable logistic, linear and Cox proportional hazards regression models were used to assess the influence of the Charlson Comorbidity Index (CCI) on survival to hospital discharge, 12-month functional recovery and health-related quality of life (HR-QOL), and long-term mortality over an eight-year period. Results A total of 15,953 patients were included. Increasing CCI was independently associated with reduced odds of survival to hospital discharge (CCI = 1: OR = 0.87 [95% CI 0.76-1.00]; CCI = 2: OR = 0.80 [95% CI 0.68-0.94]; CCI = 3: OR = 0.62 [95% CI 0.50-0.78]; CCI ≥ 4: OR = 0.53 [95% CI 0.41-0.68]). Additionally, increasing CCI was associated with reduced odds of 12-month functional recovery, a reduced chance of favourable 12-month HR-QOL, and an increased hazard of mortality after discharge from hospital. Conclusion Consideration of a patient's baseline comorbidity may assist prognostication decisions for cardiac arrest patients. Exploration of the effect of additional rehabilitation on HR-QOL and long-term survival outcomes for OHCA patients with a high baseline comorbidity burden may be warranted.