Fig. 5.

Crude and adjusted association of population density and 30-day survival. Reference group = Low population density (<300/km²). Logistic regression analysis for the association of population density and 30-day showing the crude and the adjusted odds for 30-day survival in groups of population density: medium (300–1499/km²), high (1500–2999/km²) and very high (>3000/km²) were analyzed in reference to low (<300/km²). The adjusted analyses were adjusted for age, gender, calendar year, comorbidities from baseline Table 1 and EMS response time. Odds ratio >1.00 indicates that patients in areas of medium, high and very high population densities in reference to low are positively associated with 30-day survival. CPR, cardiopulmonary resuscitation; EMS, emergency medical service; OHCA, out-of-hospital cardiac arrest; OR, odds ratio.