WISH Technical Notes and Definitions: Injury Death Data

Technical notes

All injury mortality statistics from 1999 through the current year are based on codes in the International Classification of Diseases, 10th Revision (ICD-10). ICD-10 is a medical classification created by the World Health Organization and is in use by countries worldwide. The ICD-10 includes code sets for types of disease, medical procedures, and external causes of injury.

The injury mortality subset of data is limited to only those deaths with an ICD-10 injury code as the underlying cause of death.

Numbers and rates for specific injury types

Numbers and rates for specific types of injury deaths are based on underlying cause of death coding. The exception is for traumatic brain injury (TBI), which includes review of the contributing causes for manner of injury.

Rank vs specific injury counts and rates

Rank: If the Ranking Measure is selected (Step 1), a death will only count as one type of injury based on the following groupings:

  • Drowning
  • Cutting/piercing objects
  • Falls
  • Firearm
  • Fire-heat-chemical burns-hot object/scalding
  • Machinery
  • Motor vehicle
  • Natural/environmental factors
  • Non-traffic transportation injury
  • Overexertion
  • Poisoning
  • Struck by or against object or person
  • Suffocation

Deaths classified as "other specified classifiable cause of injury," "other specified cause of injury, not elsewhere classifiable," and “unspecified cause of injury” are not included in this ranking option. These deaths are included in the ALL Injuries option in Step 2 of the query if you want a total count or rate of injury deaths.

For a breakdown of ICD-10 codes included in the above 13 categories, see groups of underlying causes of injury deaths.

Specific injuries: Specific injuries listed in Step 2 of the query do NOT include all possible injury types or causes. If you are interested in a total count or rate of all injury deaths, you can select the first option in Step 3: “ALL injuries.” For specific injury types and causes, review the rest of the list and select the option that suits your needs. The program will limit how many you can select for any one query because the options are NOT mutually exclusive and a death may be included in one or more injury types listed. For example, a motor vehicle death may also be included as a traumatic brain injury death.

In addition to this, some ICD-10 codes include injury cause and manner of death in a single code. If the underlying cause of death is recorded as “intentional self-harm by firearm discharge” (ICD-10 code X72, for example), this death is counted both as a suicide (manner) and a firearm (cause) death. In the ranking option, it is only counted as a firearm death as manner of death (suicide) is not detailed for ranking purposes.

If you are interested in the ICD-10 codes included for each injury cause and manner in Step 2, please see groups of underlying causes of injury deaths that include manner/intent. The exception is "unintentional drowning" which includes the codes V90 and V92 (accident due to watercraft or water-transport-related drowning). If you are interested in the codes used to classify Traumatic Brain Injury, please see Traumatic Brain Injury ICD-10 Codes.

Definitions

Rates

Injury mortality rates

The injury mortality rates are calculated by dividing the number of injury-related deaths per year by the population. It is usually expressed as the number of deaths per 100,000 residents. The rate may refer to a specific group, or to death from a specific cause, or to all injury deaths in the entire population. The rate may be adjusted for the age composition of the group (age-adjusted) or it may be the observed rate (unadjusted).

Unadjusted rates

This is the observed rate and is displayed as the number of deaths per 100,000 residents. We calculate this rate by dividing the number of injury-related deaths by the total population of interest and then multiply by 100,000. We recommend that you use this rate when describing injury among your population of interest (for instance, the rate of deaths from unintentional falls in Rock County). This rate should not be used to compare different populations or time periods to each other as we have not adjusted these rates to account for differences in age composition across populations or time periods.

Age-specific rates

If you want to compare rates across groups or populations for a specific age group (for example, children ages 1-4, by race), comparing observed, age-specific rates may be your best option. If this is what you want to do, select Unadjusted Rate in Step 1 and also select your one age group of interest from Age Group 1 (Step 5). An age-specific rate is calculated by dividing the total number of events for the specific age group of interest by the total population of that age group. This calculation is the same as an observed rate for the age group selected.

Alternatively, if you want to combine multiple age groups (from either Age Group option in Step 5) and compare across populations, geography, or time, we recommend selecting age-adjusted rather than age-specific rates, as age distributions can vary greatly.

Age-adjusted rates

This is a standardized rate. We recommend that you select age-adjusted rates when making comparisons between two populations (for example, Southern Region injury rates compared to Northern Region injury rates), or two different time periods (for example, 2010 injury rates compared to 2015). Age-adjustment accounts for differences in age composition across populations and time. We use the Standard U.S. Population for Year 2000 for age-adjustment.

We also recommend selecting age-adjusted rates if you want to compare across geography or time for a wide age range (a range larger than a single age category listed in Age Group 1 in Step 5). For instance, if you want the rate of injury for women of child-bearing age (15-44), and to compare rates over time, select age-adjusted rates for your Data Measure. Next, in Step 5 (Patient Characteristics), select the multiple age categories that combine to match the 15-44 age range of interest.

The age groups used to create the age-adjusted rates are those in Age Group 1 of Step 5.

Race and ethnicity

The population estimates used as denominators for the injury mortality rates in WISH are based on the bridged race estimates provided by the U.S. Census Bureau and the National Center for Health Statistics (NCHS). The estimates have been controlled so they sum to the annual estimates published by the Office of Health Informatics.

Producing the bridged race estimates was necessary because race categories in Census 2000 differed from those used in previous years. Specifically, data on race from Census 2000 were not directly comparable to data from previous years due, in large part, to giving respondents the option to report more than one race.

As a result, NCHS and the Census Bureau produced bridged race estimates that allow calculation of rates by race and ethnicity across years. These estimates distribute (or "bridge") the "more than one race" and "some other race" populations into one of four major race groups (American Indian/Alaska Native, Asian/Pacific Islander, Black, and White) and two ethnicity groups (Hispanic/Latino, non-Hispanic/Latino).

NCHS and the Census Bureau have produced this set of bridged race estimates extending back to the 1990 Census.

Last Revised: May 20, 2019