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1EPI 2670: Injury EpidemiologyTransportation Related InjuriesThomas Songer, PhDUniversity of PittsburghRoad traffic accidents are a part of everyday life. They range from minor “fender-benders” to horrific crashes, such as the one that killed Princess Diana. In the extreme, motor vehicle accidents attract our morbid attention. Injuries from motor vehicle accidents represent a significant burden in the United States and the world. In 1990, traffic accidents were the 9th leading cause of death worldwide. Their frequency is expected to increase, where in the year 2020, they are projected to be the 5th leading cause of death (Source: World Health Report, 2008).While the picture may appear bleak, there is room for optimism. Injury research, injury surveillance, and injury control in the transportation area is far advanced relative to other injury categories. Integrated efforts have dramatically decreased the impact of crashes in the western world. Further, efforts are underway to extend this practice to the developing world.2Types of TransportationMotor vehicle crashes pertain to a variety of means of transportation. Foremost, road traffic accidents involve automobiles, but the term also includes events related to small and large trucks, buses, motorcycles, and collisions between vehicles and pedestrians.3Top Ten Public Health AchievementThe reduction in the rate of death attributable to motor-vehicle crashes has been called one of the most successful public health responses to a great technologic advance of the 20th century--the motorization of America. Six times as many people drive today as in 1925, and the number of motor vehicles in the country has increased 11-fold since then to approximately 215 million. The number of miles traveled in motor vehicles is 10 times higher than in the mid-1920s. Despite this steep increase in motor-vehicle travel, the annual death rate has declined from 18 per 100 million vehicle miles traveled (VMT) in 1925 to 1.7 per 100 million VMT in 1997--a 90% decrease. Injury control efforts and epidemiology have had a large part in this decline.Achievements in Public Health, 1900-1999 Motor-Vehicle Safety: A 20th Century Public Health Achievement. MMWR May 14, 1999 / 48(18);369-3744History of Crashes05101520251935194019451950195519601965197019751980198519901995USA PennsylvaniaFatality Rate per 100 Million Vehicle MilesThe International Red Cross, in the World Disaster Report, has characterized the last 100 years as the “Century of road death”. The first pedestrian death was noted in 1896 and the first driver died in a crash in 1898. In the developed world, though, this situation has been continuously improving. The figure notes much lower rates of motor vehicle fatalities in the 1990’s than in the 1930’s. Injury control efforts and epidemiology have had a large part in this decline.Source: International Federation of Red Cross and Red Crescent Societies. World Disaster Report, 1998. Oxford University Press, Oxford 1998.This graph also points out a lesson from the lecture on comparing injury statistics. Remember that having information on trends over time is important for identifying “hot spots”, or areas where strong increases or strong declines have been observed. These areas provide possible clues to associations with crashes. Though it is not easily apparent in this slide, the period from 1973-1975 shows a meaningful decline in crash fatalities. This coincided with a decline in maximum speed limits to 55 mph. When comparing data over time, though, remember that it is also important to demonstrate that the data were gathered in a similar fashion. Comparing statistics that are based on different methods is not meaningful.5Studying the Epidemiology of Injuries from Crashes6The Accident Triumvirate•Environment•Vehicle •DriverEpidemiologic efforts to study injuries from crashes have followed the same basic framework for the last 40 years. This framework considers crash events as an interaction of three factors; the host (driver), the agent (vehicle), and the environment. Driver factors represent the human element behind accidents. It describes how the characteristics and traits of the driver may affect both crashes and injuries from crashes. The vehicle is viewed as the mechanism for energy transfer in motor vehicle accidents. The characteristics of the vehicle, such as weight and design, may influence crashes and injuries. Environmental factors represent the weather or road conditions surrounding the event and their relationship to crashes and injuries. The accident triumvirate points out that accidents are not just due to one event, but are multi-factorial. That means that several circumstances come together at the time of the crash. The notion of accidents as being a matter of fate arises from this view. However, remember that it is possible to intervene on these circumstances to either reduce the likelihood for a crash or the severity of injuries involved. Crashes are entirely preventable.7The Crash Sequence• Pre-crash Period• Crash Period• Post-crash PeriodWilliam Haddon also spoke of the “Crash Sequence” as being meaningful for studying injuries from motor vehicle accidents. This sequence involves events which occur prior to the crash, the circumstances surrounding the crash itself, and the situation that exists after the crash. Haddon argued that there are circumstances in the period of time right before the collision that may dictate whether a crash or injury from a crash happens. The characteristics of the crash itself, (i.e., how energy is transferred) influences the likelihood for and severity of injury. Third, the events which take place after a crash occurs can determine the outcome of a crash. For example, the ability to extricate victims from the car, the response time of EMS (Emergency Medical Services) to the accident scene, and the type of medical care received may all influence the injury outcome of a crash.8The Haddon Matrixuse for planning, resource allocation, strategy identificationHuman Vehicle EnvironmentPre-eventEventPost-eventThe Haddon Matrix highlights the important finding that the temporal events of the crash (it’s sequence) and it’s epidemiologic components (the triad) can be viewed together. In other words, Haddon argued that the analysis of crashes should consider these two schemata together. There are human, vehicular, and environmental factors


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Pitt EPIDEM 2670 - Epidemiology

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