Background
Survival from out‐of‐hospital cardiac arrest (OHCA) varies across regions. The aim of this study was to evaluate the association between urbanization (rural, suburban, and urban areas), bystander interventions (cardiopulmonary resuscitation and defibrillation), and 30‐day survival from OHCAs in Denmark.

Methods and Results
We included OHCAs not witnessed by ambulance staff in Denmark from January 1, 2016, to December 31, 2020. Patients were divided according to the Eurostat Degree of Urbanization Tool in rural, suburban, and urban areas based on the 98 Danish municipalities. Poisson regression was used to estimate incidence rate ratios. Logistic regression (adjusted for ambulance response time) tested differences between the groups with respect to bystander interventions and survival, according to degree of urbanization. A total of 21 385 OHCAs were included, of which 8496 (40%) occurred in rural areas, 7025 (33%) occurred in suburban areas, and 5864 (27%) occurred in urban areas. Baseline characteristics, as age, sex, location of OHCA, and comorbidities, were comparable between groups. The annual incidence rate ratio of OHCA was higher in rural areas (1.54 [95% CI, 1.48–1.58]) compared with urban areas. Odds for bystander cardiopulmonary resuscitation were lower in suburban (0.86 [95% CI, 0.82–0.96]) and urban areas (0.87 [95% CI, 0.80–0.95]) compared with rural areas, whereas bystander defibrillation was higher in urban areas compared with rural areas (1.15 [95% CI, 1.01–1.31]). Finally, 30‐day survival was higher in suburban (1.13 [95% CI, 1.02–1.25]) and urban areas (1.17 [95% CI, 1.05–1.30]) compared with rural areas.

Conclusions
Degree of urbanization was associated with lower rates of bystander defibrillation and 30‐day survival in rural areas compared with urban areas.