WEDNESDAY, Feb. 11, 2015 (HealthDay News) -- Smoking may be killing more people than even current estimates indicate, a new study suggests.
According to the U.S. Surgeon General, about 480,000 Americans die of smoking-related causes each year, but that figure may be closer to 540,000, researchers from the American Cancer Society report.
While lung cancer takes the largest toll in smoking-related deaths, the additional 60,000 deaths appear to be caused by diseases not typically associated with tobacco, including kidney failure, intestinal disease, heart disease caused by high blood pressure (hypertension), infections, breathing problems, and breast and prostate cancer, they noted.
"The Surgeon General's report claims 480,000 deaths directly caused by smoking, but we think that is really quite a bit off," said lead researcher Brian Carter, an epidemiologist at the cancer society.
"Sixty thousand [extra] deaths is really a lot," he said. "That's more than the number of people killed each year by flu or motor vehicle accidents."
The report was published Feb. 12 in the New England Journal of Medicine.
"Though we've made great gains in reducing rates of smoking, tobacco control needs to remain a top health priority. We cannot rest on past tobacco control successes," said Dr. Graham Colditz, a professor of surgery at the Washington University School of Medicine in St. Louis and author of an editorial that accompanied the study.
Tobacco needs to remain a top health priority, he said.
"It is the primary cause of preventable disease and death," Colditz said. "And we need to continue to build on the progress we've made and work toward a future endgame for tobacco -- a time when it is all but eliminated as a health issue."
Carter's team used data from five large databases that included nearly 1 million men and women aged 55 and older.
During about 10 years of follow-up, more than 180,000 people died. The death rate among people who smoked was three times higher than among those who never smoked. Most of those deaths were the result of diseases known to be related to smoking, such as certain cancers, heart disease, stroke and chronic obstructive pulmonary disease (COPD).
However, about 17 percent of the deaths in smokers were due to diseases that were not established as caused by smoking by the U.S. Surgeon General. Thus these deaths are not counted in estimates of the deaths from smoking, Carter said.
Carter said that smoking was associated with at least a doubling of risk of death from several causes, including kidney failure, intestinal diseases, hypertensive heart disease, infections and respiratory diseases other than COPD.
The risk of death from these diseases dropped after quitting smoking, the researchers found. Carter added that there is good evidence that smoking is a cause of death from these diseases, even though they are not yet included in estimates of deaths from smoking.
In addition, smoking was linked with small increases in risk of death from breast cancer, prostate cancer and other cancers, he said.
Dr. Norman Edelman, a senior consultant for scientific affairs at the American Lung Association, said, "This study tells us that we have a huge amount of work to do in terms of controlling the use of tobacco."
Edelman added that it's never too late to quit cigarettes. "Stopping smoking at any time, even if you are old and sick, will extend your life," he said. "Don't smoke. Don't let kids start smoking."
Visit the U.S. Centers for Disease Control and Prevention for more on smoking.