title: Population density, call-response interval, and survival of out-of-hospital cardiac arrest.
abstract: BACKGROUND
  Little is known about the effects of geographic variation on outcomes of out-of-hospital cardiac arrest (OHCA). The present study investigated the relationship between population density, time between emergency call and ambulance arrival, and survival of OHCA, using the All-Japan Utstein-style registry database, coupled with geographic information system (GIS) data.
  
  
  METHODS
  We examined data from 101,287 bystander-witnessed OHCA patients who received emergency medical services (EMS) through 4,729 ambulatory centers in Japan between 2005 and 2007. Latitudes and longitudes of each center were determined with address-match geocoding, and linked with the Population Census data using GIS. The endpoints were 1-month survival and neurologically favorable 1-month survival defined as Glasgow-Pittsburgh cerebral performance categories 1 or 2.
  
  
  RESULTS
  Overall 1-month survival was 7.8%. Neurologically favorable 1-month survival was 3.6%. In very low-density (<250/km(2)) and very high-density (≥10,000/km(2)) areas, the mean call-response intervals were 9.3 and 6.2 minutes, 1-month survival rates were 5.4% and 9.1%, and neurologically favorable 1-month survival rates were 2.7% and 4.3%, respectively. After adjustment for age, sex, cause of arrest, first aid by bystander and the proportion of neighborhood elderly people ≥65 yrs, patients in very high-density areas had a significantly higher survival rate (odds ratio (OR), 1.64; 95% confidence interval (CI), 1.44 - 1.87; p < 0.001) and neurologically favorable 1-month survival rate (OR, 1.47; 95%CI, 1.22 - 1.77; p < 0.001) compared with those in very low-density areas.
  
  
  CONCLUSIONS
  Living in a low-density area was associated with an independent risk of delay in ambulance response, and a low survival rate in cases of OHCA. Distribution of EMS centers according to population size may lead to inequality in health outcomes between urban and rural areas.
authors.affiliation: Department of Health Management and Policy, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan. yasunagah-jyo@h.u-tokyo.ac.jp
authors.forename: Hideo
authors.initials: H
authors.lastname: Yasunaga
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Miyata
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Horiguchi
authors.forename: Seizan
authors.initials: S
authors.lastname: Tanabe
authors.forename: Manabu
authors.initials: M
authors.lastname: Akahane
authors.forename: Toshio
authors.initials: T
authors.lastname: Ogawa
authors.forename: Soichi
authors.initials: S
authors.lastname: Koike
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Imamura
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016887:Cardiopulmonary Resuscitation / Q000592:standards / Q000639:trends; D004632:Emergency Medical Services / Q000592:standards* / Q000639:trends; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000401:mortality* / Q000628:therapy*; D011156:Population Density; D011446:Prospective Studies; D012042:Registries; D015996:Survival Rate / Q000639:trends; D013997:Time Factors; D016896:Treatment Outcome