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APHA-2006: Session 5108 1 Choice of denominator to measure disparities in motor vehicle crash deaths of teens and young adults Christopher J. Mansfield,

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Presentation on theme: "APHA-2006: Session 5108 1 Choice of denominator to measure disparities in motor vehicle crash deaths of teens and young adults Christopher J. Mansfield,"— Presentation transcript:

1 APHA-2006: Session Choice of denominator to measure disparities in motor vehicle crash deaths of teens and young adults Christopher J. Mansfield, PhD & Satomi Imai, PhD* East Carolina University Greenville, NC 134th Annual APHA Meeting November 4-8, 2006 * Presenter

2 APHA-2006: Session Objectives Examine regional, racial/ethnic, and gender disparities in motor vehicle crash deaths for teens and young adults in North Carolina. Compare motor vehicle crash (MVC) mortality rates for the young drivers using two measures - per population and per licensed drivers Identify vulnerable populations to whom interventions should be targeted for motor vehicle crash deaths

3 APHA-2006: Session Acknowledgement Center for Highway Research, UNC Chapel Hill for data on the number of young licensed drivers in NC.

4 APHA-2006: Session Background Over the past 5 years, 24% of drivers and 30% of passengers who died in motor vehicle crushes in NC were ages The number of deaths is highly disproportionate considering this age group represents 12% of the total population. Mortality rates due to MVC for ages, 16-24, have increased since 2000 in NC despite the enactment of graduated licensing law. Healthy People 2010 and Healthy Carolinians 2010 have not identified disparities as specific problems to be addressed for young deaths by MVC.

5 APHA-2006: Session Typically, MVC mortality rates are expressed as deaths per population (e.g., Healthy People 2010). However, risks for fatal crashes may differ according to age, race/ethnicity, and region for young population because of varied exposure to motor vehicles. –Age: Teens (15-19) drive fewer miles than yr olds, who drive fewer miles than yr olds. –Race: African Americans drive less than whites (2001 National Household Travel Survey)

6 APHA-2006: Session Miles or hours driven is an appropriate denominator to examine MVC mortality risk for young drivers. –19 year-olds had a highest MVC mortality rate per population, but –16 year-olds’ MVC mortality rate per 100 million vehicle miles traveled was 1.4 times higher than 18 yr olds’ and 2.2 times higher than yr olds’. (Fatality facts 2004, Insurance Institute for Highway Safety) However, data on miles driven at the state/county level by race/ethnicity are not available. An alternative: The number of licensed drivers for the denominator.

7 APHA-2006: Session We suspect that disparities by race/ethnicity exist but are underestimated by conventional definition of mortality rate. We compare here the difference in young adult MVC mortality rates calculated per population to rates per licensed drivers in NC by race/ethnicity, region, and gender.

8 APHA-2006: Session Methods Analyzed MVC death data in NC for ages for a 5-year period, *from the North Carolina State Center for Health Statistics MVC mortality rates –Per 100,000 population *from the National Center for Health Statistics –Per 100,000 NC licensed drivers *from the UNC Highway Safety Research Center

9 APHA-2006: Session We looked at MVC mortality rates for young drivers in NC by: Race/Ethnicity: Whites, African Americans, Native Americans, and Hispanics 41 Eastern Counties Gender: Male vs. Female

10 APHA-2006: Session Results

11 APHA-2006: Session

12 APHA-2006: Session MVC mortality rates per population vs. per licensed drivers

13 APHA-2006: Session MVC mortality rates per population –Peak at age 19, then gradual decline to age 24. MVC mortality rates per licensed drivers –Highest at 16 yrs old, drop at age 17, gradual decline to age 24. The use of mortality rates per population underestimates the MVC death risks for teen drivers

14 APHA-2006: Session Racial/ethnic disparities assessed by different mortality rate definitions

15 APHA-2006: Session Substantial differences, particularly for Native Americans.

16 APHA-2006: Session Disparities are much more substantial when measured by the licensed driver rate

17 APHA-2006: Session When using Licensed Drivers as the denominator, for 17 year olds, disparity ratio compared to Whites changes: Native Americans – from 3.5:1 to 8.1:1 Hispanics – from 0.8:1 to 5.5:1 African-American – from 0.5:1 to 1.3:1

18 APHA-2006: Session Regional disparity Eastern NC vs. the rest of the state

19 APHA-2006: Session Regional disparity

20 APHA-2006: Session

21 APHA-2006: Session Eastern NC has much higher MVC mortality rates than the rest of the state. Minority drivers in eastern NC are particularly vulnerable to MVC deaths. –MVC mortality rates for Native American and Hispanic drivers in eastern NC were more than two times higher than white drivers in the same region.

22 APHA-2006: Session Gender disparity 2.7 times more males (1256) died of MVC than females (470) in NC, Males and females have similar rates of obtaining a driver’s license, thus gender disparity is comparable between mortality rates per population and per licensed driver.

23 APHA-2006: Session Yearly trend

24 APHA-2006: Session Since 2000, MVC crash mortality rates of young drivers in NC have increased each year regardless of the denominator used marked the highest mortality rate per licensed drivers in the past 5 years, 45% increase from 2000 in eastern NC and 24% increase from 2000 in NC. MVC mortality rates for teen drivers, especially 16 yr old drivers, have been increasing since 2000.

25 APHA-2006: Session Teen drivers’ mortality rates increased radically from 2000 to 2004 (80% increase).

26 APHA-2006: Session Limitations Caution is needed for the interpretation of results in this presentation. –The data might not be reliable due to the small number of deaths among Native American and Hispanic drivers. –Accuracy of reporting race/ethnicity in death records. –Accuracy of population estimates for minority populations, especially Hispanics.

27 APHA-2006: Session Conclusions MVC mortality rates per licensed drivers for young drivers show wider disparities by race/ethnicity and region than those per population. MVC death risk for teen and minority drivers is underestimated by the use of mortality rate per population.

28 APHA-2006: Session In particular, 16 year-old drivers, and young Native American and Hispanic drivers had tragically high rates for MVC deaths. Young African American drivers had a similar MVC mortality rate to young white drivers when licensed drivers were used as the denominator. Despite the enactment of the graduated licensing law, the mortality rate for 16 year old drivers has increased.

29 APHA-2006: Session For additional information,


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