Smoking Continues to Kill Millions Worldwide

A second study spots a gene mutation linked to nicotine addiction

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HealthDay Reporter

WEDNESDAY, Nov. 24, 2004 (HealthDayNews) -- Deaths from smoking continue to rise around the world, and a mutation in a gene linked to nicotine metabolism may be a cause of nicotine addiction, according to two new studies in the November issue of Tobacco Control.

Smoking was responsible for almost 5 million deaths worldwide in 2000, or about 12 percent of all deaths, according to one of the studies. More than half the deaths were among smokers 30 to 69 years of age.

"In a paper a year ago we showed that smoking accounted for 4.83 million premature deaths around the world," said study co-researcher Majid Ezzati, an assistant professor of international health at the Harvard School of Public Health. "This paper looks at how these deaths are distributed around the world."

Ezzati and his colleague, Alan Lopez from the School of Population Health at the University of Queensland, Australia, used deaths from lung cancer as a measure of smoking deaths. The researchers attributed the use of coal for cooking and heating in poorly ventilated housing to explain most lung cancer deaths among nonsmokers.

They also estimated deaths from smoking due to other diseases, including throat cancers, other cancers, chronic obstructive pulmonary disease (COPD), other respiratory diseases, cardiovascular diseases, and other medical causes.

Ezzati and Lopez found that of the 4.83 million premature deaths linked to smoking, 2.41 million were in developing countries and 2.43 million were in industrialized countries. Men accounted for 3.84 million of those deaths.

The leading causes of death from smoking in industrialized countries were cardiovascular diseases, lung cancer and COPD. In developing countries, the leading causes of smoking deaths were from cardiovascular diseases, COPD, and lung cancer.

According to Ezzati, the areas where deaths from smoking are increasing the fastest are China, India, South America and Eastern Europe. In those areas, "deaths from smoking are catching up to smoking deaths in industrialized countries," he said.

"Smoking magnifies the risk for disease that already exists," Ezzati said. For example, in developing countries such as China, cooking and heating homes with wood and coal is common. That causes very high levels of chronic lung disease, he explained. "Smoking magnifies this background risk," Ezzati said.

In Eastern Europe and India, cardiovascular diseases have high background levels, and these are amplified by smoking, he noted.

The researchers plan on using their study as a base to study trends in smoking-related deaths in the future. Ezzati said that smoking-related deaths have been rising globally. They have also been increasing among women, he added.

While smoking rates have gone down in North American and Australia, Ezzati expects the upward trend in smoking-related deaths to continue elsewhere, especially in developing countries. Since smoking rates have risen in developing countries, death rates will catch up over the next several decades, he said.

"Smoking is no longer a western problem, it's definitely a global problem," Ezzati said.

"That more than 10 percent of the total number of deaths that occur on this planet each year is attributable to tobacco is nothing less than appalling," said Dr. David L. Katz, an associate clinical professor of public health from Yale University School of Medicine. "Use of tobacco is avoidable, the deaths and suffering caused preventable, yet this scourge continues to be actively peddled to consumers worldwide," he added.

"Tobacco remains a global public health scourge," Katz said. He believes that everything possible should be done to stop its use worldwide. "Pain and suffering are not bound by national borders; neither, then, should our public health efforts stop at our border," he stressed.

For the nicotine study, Canadian researchers collected data on about 1,200 seventh-graders. The research team gathered information on smoking habits and nicotine dependence. They also took blood samples to determine the students' genetic profile.

Among 228 teens who smoked but were not addicted, the researchers followed them for an average of two years.

Over two years, 67 of these students became addicted to nicotine. O'Loughlin's group found that those with a mutation of the CYP2A6 gene, which controls nicotine metabolism in the liver, were more likely to become addicted, compared with those who did not have a mutation of this gene. About 6 to 8 percent of the population has this genetic mutation, according to the researchers.

"What we have found is that people metabolize nicotine either quickly or slowly," said lead researcher Jennifer O'Loughlin, an assistant professor of epidemiology from McGill University. "And this is under genetic control."

"People who metabolize nicotine slowly appear to become nicotine-dependent much quicker," O'Loughlin said. The risk for becoming nicotine-dependent is three times higher among those who metabolize nicotine slowly than it is in people who metabolize it normally, she explained.

More information

The National Institutes of Health can tell you more about the dangers of tobacco.

SOURCES: Majid Ezzati, Ph.D., assistant professor of international health, Harvard School of Public Health, Boston; David L. Katz, M.D., M.P.H., associate clinical professor of public health, Yale University School of Medicine, New Haven, Conn.; Jennifer O'Loughlin, Ph.D., assistant professor of epidemiology, McGill University, Montreal; November 2004 Tobacco Control

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