Moderate drinking accounts for more injuries than heavy drinking does, simply because more people tend to drink small amounts, according to a new report in the Annals of Family Medicine.

Surveys of people visiting emergency departments in Missouri found that around 1 out of 10 accidents resulted from drinking alcohol. Roughly half of the injuries attributed to alcohol occurred after people had been drinking lightly - having fewer than five drinks for men, or fewer than four drinks for women.

Overall, the researchers calculate that one million injuries treated in emergency departments in 2001 alone were attributable to drinking “what has been considered a nonhazardous amount of alcohol.”

These findings suggest that the amount of alcohol considered “safe” is not completely so, study author Dr. Daniel C. Vinson, of the University of Missouri-Columbia, told Reuters Health.

However, Vinson noted that individual drinkers have a very small risk of being injured after light drinking. But since there are so many light drinkers, from the perspective of society, even having a couple of drinks becomes a problem when “all of those little, tiny risks are added together.”

Previous research has shown that downing as few as two drinks of alcohol increases the chances of getting injured, and the risk appears to increase exponentially with every additional drink.

Although individuals are more likely to become injured after drinking heavily, Vinson and his co-author Dr. Maria C. Spurling wondered if society, as a whole, is more at risk from heavy drinkers or light drinkers, who greatly outnumber those who drink heavily.

This is known as the prevention paradox, which states that there may be more danger from a large number of people who have a small risk of disease than from a small number of people who have a much higher risk of disease.

For instance, the authors argue that doctors would avoid more cases of disease if they treated the many people with mildly high levels of cholesterol than if they focused all their efforts on the few people with higher levels of cholesterol.

To determine whether the same principle applies to alcohol-related injuries, the researchers interviewed 2,517 people treated at an emergency department for severe injuries and 1,856 similar non-injured people.

They found that roughly the same number of injuries stemmed from heavy and light drinking, suggesting that, when it comes to preventable injuries, both behaviors have roughly the same impact on society.

Overall, the researchers calculate that between 900,000 and 1.3 million people end up in emergency rooms each year after drinking relatively small amounts of alcohol.

In an interview, Vinson noted that, as a 150 pound man, he would have to down 5 drinks in 1 hour on an empty stomach to reach most state’s blood alcohol limit for driving, 0.8.

These findings suggest that people may be impaired from much less alcohol, and drivers should take extra precautions even if they are within the law.

“Be aware that if you drink two, three, or four drinks you are slightly increasing your risk of injury,” Vinson advised. “Be more careful.”

SOURCE: Annals of Family Medicine, January/February 2005.