Regional variation in out-of-hospital cardiac arrest: Incidence and survival - A nationwide study of regions in Denmark

AIM: Regional variation in incidence and survival after out-of-hospital cardiac arrest (OHCA) may be caused by many factors including differences in definitions and reporting. We examined regional differences in Denmark.

METHODS: From the Danish Cardiac Arrest Registry we identified adult OHCA patients between 2009-2014 of presumed cardiac cause. Patients were grouped according to the five administrative/geographical regions of Denmark and survival was examined based on all arrest-cases (30-day survival percentage) and number of survivors per 100,000 inhabitants.

RESULTS: We included 12,902 OHCAs of which 1550 (12.0 %) were alive 30 days after OHCA. No regional differences were observed in age, sex or comorbidities. Incidence of OHCA ranged from 32.9 to 42.4 per 100,000 inhabitants; 30-day survival percentages ranged from 8.5% to 13.8% and number of survivors per 100,000 inhabitants ranged from 3.5 to 5.9, across the regions. In one of the regions car-manned pre-hospital physicians were discontinued from 2011. Here, the incidence of OHCA per 100,000 inhabitants increased markedly from 37.1 in 2011 to 52.2 in 2014 and 30-day survival percentage decreased from 10.9 % in 2011 to 7.5 % in 2014; while the number of survivors per 100,000 inhabitants stagnated from 4.0 in 2011 to 3.9 in 2014. In comparison, survival increased in the other four regions.

CONCLUSION: Differences in incidence and 30-day survival after OHCA were observed between the five regions of Denmark. Comparisons of survival should not only be based on survival percentages, but also on number of survivors of the background population as inclusion bias can influence survival outcomes.