The news appears in the March issue of the American Journal of Preventive Medicine.
In the study, researchers surveyed nearly 15,000 adult smokers in the U.S., U.K., Canada, and Australia to test the effectiveness of the warning labels used in those four countries. The surveys were conducted between 2002 and 2005.
The key finding: The U.S. labels, which were the smallest and least detailed, were also the least effective.
"The current findings, along with previous research, suggest that U.S. smokers might benefit from large graphic warnings on cigarette packages," write the researchers, who include David Hammond, PhD, of Canada's University of Waterloo.
U.S. cigarette labels include four warnings written on the side of cigarette packages.
Canadian, Australian, and British cigarette warning labels are much bigger, include more health warnings, and appear on the front and back of the packages.
The Canadian label covers half of the front and back of cigarette packages. It includes 16 warnings in print as well as pictures, such as a graphic suggestive of impotence and the words "Tobacco use can make you impotent."
The Australian label includes six written warnings but no pictures. It covers a quarter of the front and a third of the back of cigarette packages.
The U.K. revised its cigarette warning label in late 2002, adding 10 written warnings (such as "Smoking when pregnant harms your baby") for a total of 16 written warnings on the front and back of the package. The warning text was also enlarged at that time.
World of Warnings
Some other countries get even more graphic with their warning labels, according to the report.
For instance, a Thai label includes a picture of a man smoking, with skulls floating in the background.
A Brazilian label shows an unhappy couple in bed, with a warning about impotence from smoking.
Another label image proposed (but not required) by the European Union is a drawing of a dead man, his eyes covered by a cloth, lying on a table. The words "Smokers die younger" appear next to that image.
Hammond's team didn't analyze the effectiveness of those labels.
In the surveys, Hammond's team asked smokers in the four countries studied how often they noticed the warning labels on cigarettes and whether the labels made them try to quit smoking or think about smoking's health risks.
U.S. smokers -- who had the smallest, least-detailed warning labels -- were the least likely to report noticing or reacting to the labels.
"The U.S. warnings performed poorly compared to those in other countries," write Hammond and colleagues.
In contrast, Canadian smokers -- who had the biggest, most graphic warning labels of the four countries -- reported the greatest impact from those labels.
Australia ranked second, followed by the U.K.
But the British label change made an impact on smokers, boosting their awareness and quit-smoking attempts -- at least at first.
That effect faded within two and a half years after the label change, probably because British smokers had gotten used to the new label, Hammond's team notes.
Bigger May Be Better
U.S. warning labels may need a makeover to become more effective, the study suggests.
"The health warnings that appear on the side of U.S. cigarette packages provide even less health information than many other, more benign consumer goods," write Hammond and colleagues.
They point out that quit-smoking tips and encouragement are packed inside Canadian cigarette packages.
Putting quit-smoking resources (such as web sites and toll-free smoking cessation phone lines) on cigarette packages might also help, Hammond's team uggests.
SOURCES: Hammond, D. American Journal of Preventive Medicine, March 2007; vol 32: pp 210-217. News release, Elsevier Health Sciences.
By Miranda Hitti
Reviewed by Louise Chang