Population density and mortality among individuals in motor vehicle crashes
- Rolf Gedeborg1,2,
- Ingemar Thiblin3,
- Liisa Byberg2,4,
- Håkan Melhus5,
- Johan Lindbäck6,
- Karl Michaelsson2,4
- 1Department of Surgical Sciences, Anaesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden
- 2Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden
- 3Department of Surgical Sciences, Forensic Medicine, Uppsala University, Uppsala, Sweden
- 4Department of Surgical Sciences, Orthopaedics, Uppsala University, Uppsala, Sweden
- 5Department of Medical Sciences, Uppsala University, Uppsala, Sweden
- 6Biometrics Section, Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden
- Correspondence to Dr Rolf Gedeborg, Uppsala University, UCR/Scheele, Dag Hammarskjölds väg 50A, 3tr, Science Park, SE-751 85 Uppsala, Sweden;
- Accepted 8 March 2010
- Published Online First 30 June 2010
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.
Funding This study was supported in part by the Laerdal Foundation for Acute Medicine, LPS Medical Foundation and the Swedish Research Council. The study sponsors had no involvement in the study design, in the collection, analysis and interpretation data, in the writing of the report, or in the decision to submit the paper for publication.
Competing interests None.
Ethics approval This study was conducted with the approval of the regional ethics committee, Uppsala University.
Provenance and peer review Not commissioned; externally peer reviewed.