Alcohol’s double threat: a greater chance of crashing, and more severe injuries

  • Alcohol is known to be a causal factor in motor vehicle crashes (MVCs).
  • New research has found that alcohol can also affect outcome after an MVC injury occurs.
  • Alcohol’s potentiating effect on injury occurs at both low and high levels of crash severity as well as both low and high levels of alcohol.

Alcohol clearly impairs judgment and performance during the operation of a motor vehicle, as evidenced by the number of injured patients treated in emergency departments (EDs). A study in the April issue of Alcoholism: Clinical & Experimental Research has found that the relationship between alcohol and motor vehicle crash (MVC) injury is even more insidious: alcohol can actually exacerbate injury.

"We wanted to know, ‘what is the impact of alcohol on injury severity if a crash occurs?’" said Ronald F. Maio, director of the Injury Research Center at the University of Michigan and one of the primary authors of the study. "It concerned us that many physicians and researchers – while acknowledging the effects of alcohol on the chance of an MVC occurring – were nonetheless uninformed, or misinformed, about the effects of alcohol on injury severity once the crash has occurred. In fact, many clinicians have said that alcohol has a ‘protective effect,’ which may lead lay people to mistakenly think that there is a ‘good side’ to driving and drinking."

"Both acute and chronic alcohol abuse have a number of adverse effects on the body that could conceivably increase the severity of an MVC injury," said Carl A. Soderstrom, associate director of the Medical Advisory Board and Driver Safety Research, Maryland Motor Vehicle Administration. "These include, but are not limited to, effects on the body’s blood clotting system that could result in an increased potential for bleeding; a decreased tolerance for low blood pressure or shock, which in the case of injury, is usually from bleeding; an increase in dangerous heart beats and rhythms from impacts to the chest, such as striking the steering column or impacts from air bags; and an increase in the amount of injury to a particular organs, such as the brain or spinal cord."

Soderstrom added that this study further distinguished itself from previous research by taking into account the severity of each victim’s crash. "This was ascertained by factoring in the amount of vehicle deformation in each crash," he said. "It is not only important to know that a car crashed into a tree, but how hard that car crashed into a tree."

In this study, researchers collected data for 1,362 motor-vehicle-crash victims, 18 years of age of older, who were treated and released, admitted to a hospital, or died following the accident. All of the victims were transported from the crash scene to one of two EDs within six hours of the crash. Data were collected for 29 months at the university hospital, and for 15 months at the community hospital.

Using regression analysis, study authors found that the best predictors of injury severity were vehicle crush, safety belt use, interaction between vehicle crush and safety belt use, and age. Alcohol use further predicted injury, increasing the victims’ score on the Injury Severity Scale by about 30 percent, all else being equal. In short, alcohol increases injury, although the effects of various alcohol levels are less clear.

"Clinical implications pertain to triage, patient evaluation, and intervention," said Maio. "Because patients who have been drinking are at greater risk for injury from a given set of injury mechanism conditions than patients who have not been drinking, triage decisions and evaluation may need to be modified based on the presence or absence of alcohol." In other words, previous consumption could very well have an effect on appropriate treatment and, possibly, recovery.

"Implications for injury prevention are substantial," said Maio. "All motor vehicle occupants who have been drinking are at increased risk for injury. Alcohol’s potentiating effect on injury occurs at low levels of crash severity as well as high, and at low levels of alcohol as well as high, suggesting that these findings may be relevant to other injury mechanisms, such as falls or assaults, which usually involve lower levels of kinetic energy. The findings further underscore the importance of clinicians taking an active role in preventing alcohol use where there is risk of injury. In addition, because excess injury from alcohol occurs even at alcohol levels below a blood alcohol concentration of 0.10 percent, previous analyses of alcohol-related injury costs may have underestimated the true cost of alcohol in MVCs."

Maio said there are two "take-home messages" from this study. "Having a designated driver is not completely adequate in protecting you from the harm that alcohol can do if you are involved in a crash," he said. "Furthermore, even if your alcohol level is well below the legal limit and you are driving, you are still increasing your chances of a serious injury if you are involved in a crash."

Funding for this Addiction Science Made Easy project is provided by the Addiction Technology Transfer Center National Office, under the cooperative agreement from the Center for Substance Abuse Treatment of SAMHSA.

Articles were written based on the following published research:

Waller, P.F., Hill, E.M., Maio, R.F., Blow, F.C. (April 2003). Alcohol effects on motor vehicle crash injury. Alcoholism: Clinical & Experimental Research, 27(4), 695-704