Background An increase has been observed in 30-day survival of out-of-hospital cardiac arrest (OHCA) in the past 18 years from 4% to 14% in Denmark, but OHCA survival remains low. We investigated how pre-existing comorbidities affected 30-day survival and time-to-death of OHCA patients.

Method This is a retrospective registry-based study with use of nationwide registries. Data on OHCA (2001–2015) were obtained from the Danish Cardiac Arrest Registry, data on the most clinically relevant comorbidities were collected from the Danish National Patient Registry and the Danish National Prescription Registry for up to 10 years prior to their arrest. Data on time-to-death was collected from the Danish Cause of Death Registry. Analysis was performed with use of several generalised linear models.

Results OHCA patients with AMI, ischemic heart disease (IHD), arrythmia, hyperlipidemia, and heart failure, had a 30-day survival of 7.39[6.87;7.95], 5.43[4.90;6.02], 2.87[2.66;3.09], 1.76[1.60;1.93] and 1.51[1.39;1.65], respectively, presented as odds ratios (OR). Patients with the co-existing conditions i) AMI and arrythmia or ii) arrythmia and IHD had an OR of 12.51[11.12;14.08] and 3.68 [3.30;4.09], respectively. In a time-to-death analysis presented as incidence rate ratios, Mental disorders due to use of alcohol 2.63[2.39;2.88], COPD and respiratory failure 2.58[2.42;2.74], stroke 1.96[1.82;2.11], cancer 1.76[1.61;1.91], infection 1.71[1.58;1.85], or diabetes 1.52[1.41;1.63] were important.

Conclusion Comorbidities significantly influence survival of OHCA patients. Cardiovascular comorbidities constitute the major part of the disease burden. The influence of comorbidity should be included in future treatment guidelines of OHCA patients.

Conflict of interest None.

Funding None.