Study: Role of alcohol in U.S. traffic deaths may be underreported on death certificates

It's no secret that drinking and driving can be a deadly mix. But the role of alcohol in U.S. traffic deaths may be substantially underreported on death certificates, according to a study in the March issue of the Journal of Studies on Alcohol and Drugs.

Between 1999 and 2009, more than 450,000 Americans were killed in a traffic crashes. But in cases where alcohol was involved, death certificates frequently failed to list alcohol as a cause of death.

Why does that matter? One big reason is that injuries are the leading cause of death for Americans younger than 45, according to the Centers for Disease Control and Prevention. And it's important to have a clear idea of alcohol's role in those deaths, explained Ralph Hingson, Sc.D., of the U.S. National Institute on Alcohol Abuse and Alcoholism.

"We need to have a handle on what's contributing to the leading cause of death among young people," Hingson said. What's more, he noted, researchers need reliable data to study the effects of policies aimed at reducing alcohol-related deaths.

"You want to know how big the problem is, and if we can track it," Hingson said. "Is it going up, or going down? And what policy measures are working?"

For the new study, I-Jen Castle, Ph.D., and a team led by Hingson focused on traffic deaths because, of all types of accidental fatalities, that's where researchers have the best data. This is partly because many U.S. states-about half right now-require that fatally injured drivers be tested for blood alcohol levels, and nationwide about 70% of those drivers are tested.

Hingson's team used a database maintained by the National Highway Traffic Safety Administration, called the Fatality Analysis Reporting System (FARS)-which contains the blood alcohol levels of Americans killed in traffic crashes. They compared that information with deaths certificate data from all U.S. states.

Overall, they found, death certificates greatly underreported the role of alcohol in traffic deaths between 1999 and 2009: Just over 3 percent listed alcohol as a contributing cause. But based on the FARS figures, 21 percent of those deaths were legally drunk.

The picture varied widely from state to state. In some states-such as Maryland, Nevada, New Hampshire, and New Jersey-alcohol was rarely listed on death certificates. Certain other states did much better, including Delaware, Iowa, Kansas, and Minnesota. It's not fully clear why alcohol is so often left off of death certificates. One reason could be the time it takes to get blood-alcohol test results back. Coroners or medical examiners usually have to file a death certificate within three to five days, Hingson's team notes, but toxicology results might take longer than that.

The reasons for the wide variation among states aren't known either. But Hingson said that's an important question. "Some states have been pretty successful," he noted. "What are they doing right?"

It doesn't seem to be only a matter of passing laws: States that mandate alcohol testing for deceased drivers did not always do better when it came to reporting alcohol as a contributor on death certificates.

Whatever the reasons, Hingson said, the role of alcohol in injury deaths may be seriously underestimated on death certificates. And the situation is likely worse with other types of accidental deaths, such as falls, drug poisoning/overdoses, and drowning, for which there is no mandatory blood alcohol testing or other reporting systems.