title: Population density and mortality among individuals in motor vehicle crashes.
abstract: OBJECTIVE
  To assess whether higher mortality rates among individuals in motor vehicle crashes in areas with low population density depend on injury type and severity or are related to the performance of emergency medical services (EMS).
  
  
  METHODS
  Prehospital and hospital deaths were studied in a population-based cohort of 41,243 motor vehicle crashes that occurred in Sweden between 1998 and 2004. The final multivariable analysis was restricted to 6884 individuals in motor vehicle crashes, to minimise the effects of confounding factors.
  
  
  RESULTS
  Crude mortality rates following motor vehicle crashes were inversely related to regional population density. In regions with low population density, the unadjusted rate ratio for prehospital death was 2.2 (95% CI 1.9 to 2.5) and for hospital death 1.5 (95% CI 1.1 to 1.9), compared with a high-density population. However, after controlling for regional differences in age, gender and the type/severity of injuries among 6884 individuals in motor vehicle crashes, low population density was no longer associated with increased mortality. At 25 years of age, predicted prehospital mortality was 9% lower (95% CI 5% to 12%) in regions with low population density compared with high population density. This difference decreased with increasing age, but was still 3% lower (95% CI 0.5% to 5%) at 65 years of age.
  
  
  CONCLUSIONS
  The inverse relationship between population density and mortality among individuals in motor vehicle crashes is related to pre-crash factors that influence the type and severity of injuries and not to differences in EMS.
authors.affiliation: Department of Surgical Sciences, Anaesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden. rolf.gedeborg@surgsci.uu.se
authors.forename: Rolf
authors.initials: R
authors.lastname: Gedeborg
authors.forename: Ingemar
authors.initials: I
authors.lastname: Thiblin
authors.forename: Liisa
authors.initials: L
authors.lastname: Byberg
authors.forename: Håkan
authors.initials: H
authors.lastname: Melhus
authors.forename: Johan
authors.initials: J
authors.lastname: Lindbäck
authors.forename: Karl
authors.initials: K
authors.lastname: Michaelsson
mesh_terms: D000063:Accidents, Traffic / Q000145:classification / Q000401:mortality*; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D004632:Emergency Medical Services / Q000592:standards*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015601:Injury Severity Score; D008297:Male; D008875:Middle Aged; D011156:Population Density; D012307:Risk Factors; D012622:Seat Belts / Q000706:statistics & numerical data; D013548:Sweden / Q000453:epidemiology; D014947:Wounds and Injuries / Q000145:classification / Q000401:mortality*; D055815:Young Adult