Estimating the effect of emergency care on early survival after traffic crashes.
BACKGROUND
Traffic crash mortality is higher in rural areas, but it is unclear whether this is due to greater injury severity, time delays, or Emergency Medical Services (EMS) deficiencies.


METHODS
Data from 2002-2003 were combined from the Fatality Analysis Reporting System (FARS) and an "expanded version" of the National Automotive Sampling System (NASS) Crashworthiness Data System (CDS). Weighted Cox and Weibull models for survival time (tSURV) were estimated, with time-varying covariates (TVC) having constant effects for specified time intervals following EMS arrival time (tEMS) and hospital arrival time (tHOS). The Weibull model was repeated with tSURV interval-censored to reflect uncertainty about the exact time of death, using an imputation method to accommodate interval censoring along with TVC.


RESULTS
FARS contained records for 92,718 persons with fatal or incapacitating injuries, and NASS/CDS contained 5517 (weighted population of 642,716) with incapacitating injuries. All models associated mortality with increasing age, male sex, belt nonuse, higher speeds, and vehicle rollover. The interval-censored model associated EMS intervention with a beneficial effect until tEMS+30 min, but not thereafter; hospital intervention was associated with a strongly beneficial effect that increased with time. Rural location was associated with a higher baseline hazard; a 50% reduction in rural prehospital time would theoretically reduce 4-h mortality by about 7%.


CONCLUSIONS
Rural/urban disparity in crash mortality is mostly independent of time delays and EMS effects. However, survival models with TVC support clinical intuition of a "golden hour" in EMS care, and the importance of timely transport to a hospital.
Maine Medical Center, Department of Surgery, 887 Congress Street, Suite 210, Portland, ME 04102, United States; Maine Medical Center, Center for Outcomes Research and Evaluation, Portland, ME, United States; Harvard School of Public Health, Harvard Injury Control Research Center, Boston, MA, United States. Electronic address: clarkd@mmc.org.
David E
DE
Clark
Robert J
RJ
Winchell
Rebecca A
RA
Betensky
D000063:Accidents, Traffic / Q000401:mortality*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016208:Databases, Factual; D004632:Emergency Medical Services / Q000706:statistics & numerical data*; D005260:Female; D006297:Health Services Accessibility / Q000706:statistics & numerical data*; D054625:Healthcare Disparities / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D016016:Proportional Hazards Models; D012423:Rural Health / Q000706:statistics & numerical data*; D019035:Rural Health Services / Q000706:statistics & numerical data*; D016019:Survival Analysis; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States; D014947:Wounds and Injuries / Q000209:etiology / Q000401:mortality / Q000628:therapy*
Emergency medicine; Interval censoring; Mortality; Motor vehicle; Survival; Time-varying covariates