Brief Explanations of Injury Data
Databases: Injury data comes from four primary sources
Vital Records: Every death in Maine is recorded by the Medical Examiner and the cause of death is stored in the Vital Records system. In Maine the Office of Data, Research and Vital Statistics maintain this database. The cause of death is coded using a coding system developed by the World Health Organization. This database can be queried to establish the leading causes of death in the State.
Universal Hospital Discharge Database: Like the death data, every hospital admission (overnight stay) is coded for the primary cause of the hospitalization. A separate coding system is used to designate the external cause of injury.
Emergency Department Database: Maine has a new emergency department database similar to the hospital discharge database.
Survey Data: Two surveys are used to measure the public response to injury issues. The BRFSS is a telephone survey of adults about a variety of issues including injury. Questions on this survey asked about seatbelt use and safe firearm storage. Maine has added questions concerning other types of injury. The YRBFS is a survey of middle school and high school youth. Questions on this survey focus safe practices (seat belt and helmet use), suicide, depression and violence in the schools.
Rates and Averages:
Rates: The number of deaths or hospitalizations is seldom charted since the information can be misleading. The number of deaths from any type of injury must be understood in relationship to the number of people in a geographic area. Therefore all injury data is displayed in rates per 100,000 people. In other words, out of 100,000 people in Maine there were 170 deaths in motor vehicle traffic crashes in 1998 for a rate of 13.66 per 100,000 people. By using rates we can examine a type of injury death across states or counties. The common notation would be 13.66/100,000. The formula is simple:
(Number of deaths/Population for a given area and age group)X 100,000
or
(170 deaths/1,244,250) X 100,000 = 13.66 per 100,000
Age Adjusted Rates: Age adjusting is a complex statistical process where the age breakdown of populations is taken into consideration. Age Adjusting statistically weighs the data to adjust to a representation of the most typical population age breakdown. For example, there are very few deaths by fall of young people, but numerous deaths by fall of the elderly. If one were to compare 1998 Maine fall deaths to 1998 Florida fall deaths, it would appear that there was about the same degree of risk in Maine with a rate of 5.47/100,000 as in Florida with a rate of 5.40/100,000. But Florida has a much greater proportion of elderly than Maine in its' population. That greater representation of elderly "skews" the Florida data. In reality, Maine citizens are at greater risk of deaths from falls. Maine's age adjusted rate for 1998 was 5.02/100,000 where Florida's was only 4.23/100/000. The most likely explanation why Maine and most rural states have a higher fall death rate is the distance to medical treatment, but this issue would have to be studied further to know for sure.
Five Year Moving Averages: Since injury and other health incidents are relatively low compared to the overall population, one death can radically "skew" a chart and make it look like a major change when there really is very little change. For example, if a county has been experiencing 10 motor vehicle deaths a year for a decade, than one car crash claims five lives, is it far to say that the motor vehicle death rate in that county has risen by 50% or is this a once in century anomaly. To account for this problem we tend to look at injury rates in five year moving averages. We would add all the deaths for 1990 to 1994 together and calculate the rate, than add all the deaths from 1991 to 1995 together and calculate the rate. In this manner we are able to determine if change has actually taken place.
