Prehospital injury deaths--strengthening the case for prevention: nationwide cohort study.

BACKGROUND

To determine the frequency and characteristics of prehospital deaths compared with hospital deaths in different subpopulations with severe injuries.

METHODS

Population-based cohort study using person-based linkage of the Swedish nationwide hospital discharge register with death certificate data. In all, 28,715 injury deaths were identified among 419,137 cases of severe injury during 1998 to 2004. Prehospital deaths were defined as autopsied out-of-hospital deaths with injury as the underlying cause. Their impact on mortality prediction was assessed using the International Classification of Disease Injury Severity Score with the C statistic as a measure of discrimination.

RESULTS

The majority of all injury deaths occurred either at the scene or before hospitalization. Among persons younger than 65 years, for each hospital death there were nine prehospital deaths. A high proportion of deaths from drowning, suffocation, and firearm injuries were prehospital (85, 82, and 67% of all cases, respectively). More than 90% of hospital deaths resulted from unintentional injuries, while only 43% of prehospital deaths were unintentional. The largest increase in a cause-specific case fatality risk estimate was seen for poisoning, where inclusion of prehospital deaths increased the risk estimate from 1.6% to 22.8%. Injury mortality prediction based on International Classification of Disease Injury Severity Score improved when prehospital deaths were added to hospital data (C statistic increased from 0.86 to 0.93).

CONCLUSIONS

Prehospital deaths constitute the majority of trauma deaths and differ in major characteristics from hospital deaths. The high proportion of prehospital deaths among young and middle aged people highlights the potential impact of preventive efforts.

LEVEL OF EVIDENCE

III.