Race, Hispanic origin, and socioeconomic status in relation to motor vehicle occupant death rates and risk factors among adults

Abstract

Black and Hispanic adults travel less in motor vehicles than whites but may be at greater risk when they do travel. Passenger vehicle occupant deaths per 10 million trips among persons ages 25–64 were computed by race, Hispanic origin, gender, and socioeconomic status (SES) using 1995 data from the Fatality Analysis Reporting System (FARS) and Nationwide Personal Transportation Survey. Educational level was used as the indicator of SES. Blacks, particularly black men, were at increased risk of dying relative to whites when traveling in motor vehicles (rate ratio (RR) for black men=1.48; 95% confidence interval (CI)=1.42–1.54). Hispanic men, but not Hispanic women, also had elevated occupant death rates, but their risk was less than that of black men (RR=1.26; 95% CI=1.20–1.31). SES was the strongest determinant of occupant deaths per unit of travel; RRs among those who had not completed high school were 3.52 (95% CI=3.39–3.65) for men and 2.79 (95% CI=2.69–2.91) for women, respectively. Whites without high school degrees had the highest death rates per 10 million trips. After adjustment for SES, the elevated risk of occupant fatalities persisted among black men and women, but not among Hispanic men.

Seat belt use and alcohol-impaired driving were examined among fatally injured passenger vehicle drivers. Among those with no education beyond high school, higher percentages were reported as having high blood alcohol concentrations (BACs) or having not used belts. Reported belt use rates were lower among black men and women, even after controlling for SES, whereas Hispanic men and women had belt use rates similar to those of whites. High BACs were more common among Hispanic men, which appeared largely to be an effect of SES because most Hispanic men killed in crashes had not completed high school, the education level with the highest percentage that drove while impaired by alcohol. More effective public health efforts are needed to reduce occupant deaths among persons of lower SES, blacks, and Hispanics, including measures to increase use of seat belts and reduce alcohol-impaired driving.

Introduction

This study examined the relationship of race, Hispanic origin, and socioeconomic status (SES) to the risk of adult motor vehicle occupant deaths per unit of travel. Belt use, alcohol-impaired driving, and other risk factors for occupant fatalities also were investigated in racial/ethnic and socioeconomic groups.

Injuries arising from motor vehicle crashes are one of the leading causes of death in the US, particularly among people ages 1–44 (Hoyert et al., 1999). Between 1975 and 1998, passenger vehicle occupant deaths per 100,000 persons declined by 17% and declined by 48% per 100 million vehicle-miles of travel (National Highway Traffic Safety Administration (NHTSA, 1999a)). These declines have been attributed to safer roads, safer vehicles, better emergency medical care, increased use of occupant restraints, airbags, and decreases in the frequency of alcohol-impaired driving (Centers for Disease Control and Prevention, 1999; NHTSA, 1999b, NHTSA, 1999c). Further progress in highway safety can be made by identifying groups with high rates of death and non-fatal injury from motor vehicle crashes, figuring out why they have increased risks, and determining effective methods of reducing their risks.

Low per capita income has been identified as a determinant of overall injury mortality (Baker et al., 1992); consequently, groups with lower average incomes such as non-Hispanic blacks and Hispanics (US Bureau of the Census, 1995, Zmud and Arce, 1999) may be at higher risk for fatal motor vehicle occupant injuries. For the remainder of this paper, the term “white” will refer to non-Hispanic whites, and the term “black” will refer to non-Hispanic blacks.

Inconsistent findings have been published concerning motor vehicle-related mortality of black and Hispanic adults. Among blacks, both increased rates of motor vehicle-related deaths per 100,000 persons (Cubbin et al., 2000, Martinez and Veloz, 1996) and non-elevated rates have been reported (Fingerhut et al., 1994). Similarly, both increased death rates (Harper et al., 2000, Martinez and Veloz, 1996) and non-elevated rates per 100,000 persons have been reported among Hispanics (Cubbin et al., 2000, Fingerhut et al., 1994).

Hispanics and blacks have lower rates of car ownership, travel less often in motor vehicles, and walk and use public transit more often than whites (Pucher et al., 1998, Zmud and Arce, 1999). Consequently, lower exposure to vehicle travel should result in lower occupant death rates per 100,000 persons. An important question is whether Hispanics and blacks are at greater risk when they do travel in vehicles. A recent study observed marked elevations in motor vehicle occupant death rates per billion vehicle-miles of travel among Hispanic male and black male teenagers relative to white male teenagers, yet white teenagers had higher occupant fatalities per 100,000 persons (Baker et al., 1998). Estimating occupant death rates per unit of travel is essential for determining risks among population groups with lower car ownership and mobility.

Controlling for SES is important in assessing whether there are racial and ethnic disparities in motor vehicle occupant fatality rates. Cubbin et al. (2000) adjusted for socioeconomic variables in an analysis of all deaths related to motor vehicles, and this adjustment removed the excess fatality risk observed among blacks. However, their findings were for overall motor vehicle-related fatalities—including vehicle occupants, pedestrians, motorcyclists, bicyclists—and did not necessarily apply to motor vehicle occupant deaths. Less vehicle travel and increased use of alternative modes of travel among blacks and Hispanics should decrease the motor vehicle occupant death rate per 100,000 population but increase the rates of non-occupant deaths. The current study includes only motor vehicle occupant deaths.

Another area needing further study is the extent to which black and Hispanic motor vehicle occupants are exposed to factors tending to increase their risk of dying in crashes. Studies on belt use among black adults are contradictory; observed use rates have been reported as higher (Williams et al., 1996) as well as lower than those of white adults (NHTSA, 1997, Preusser and Preusser, 1997). The extent of belt use among Hispanic adults also is unclear, with one study reporting comparable usage rates among whites and Hispanics (Wells et al., 2002) and another study reporting lower use rates among fatally injured Hispanic motorists in Colorado (Harper et al., 2000).

Regarding alcohol-impaired driving, previous studies have reported that Hispanics and blacks are over-represented in alcohol-related traffic crashes (Chang et al., 1996, Davies and Griffin, 1996, Popkin and Council, 1993, Ross et al., 1991). In addition, higher percentages of Hispanic drivers had elevated blood alcohol concentrations (BACs) in the 1996 National Roadside Breath Alcohol Survey (Voas et al., 1998). However, these previous findings could reflect the lower SES of Hispanics and blacks rather than other sociocultural characteristics.

This study estimates the risk of death among adult black, white, and Hispanic passenger vehicle occupants per unit of travel, whereas prior research on race and Hispanic origin in relation to motor vehicle-related mortality has reported death rates per population. Another contribution of this study is being able to distinguish socioeconomic from racial/ethnic influences on vehicle occupant mortality rates, including the distribution of risk factors for occupant death and injury.