The Associated Press
LONDON -- About half the tuberculosis deaths among men in India, which has the world's highest TB toll, are due to smoking, new research indicates.
In the first major study to identify smoking as an important cause of death from tuberculosis, researchers calculated that men in India who smoke are about four times as likely to become ill with TB and die as their nonsmoking countrymen.
They concluded that three-quarters of the smokers who became ill with TB would not have done so if they had not smoked.
The research, published this week in The Lancet medical journal, illustrates how smoking magnifies the death toll from illnesses that are already common in a region.
TB kills about 1.6 million people a year worldwide, including more than 1 million in Asia, 400,000 in Africa and 100,000 in the Americas and Europe.
"Almost 200,000 people a year in India die from TB because they smoked, and half of the smokers killed by TB are still only in their 30s, 40s or early 50s when they die," said the study's leader, Dr. Vendhan Gajalakshmi of the Epidemiological Research Center in Chennai, India.
Many previous studies on the dangers of smoking were done in developed countries, where tuberculosis deaths are rare, or in developing countries such as China where the increase in smoking is too recent for the full hazards to have materialized, said the investigators from research centers in India, Britain and Canada.
Experts at the World Health Organization said the findings indicate addressing smoking may be key to improving the success of global TB control efforts, which are focused on providing medicine. Drugs can normally cure more than 90 percent of cases and would still be needed to fight TB.
"We estimate that the death rate from TB in India is about double that of China, and smoking could explain much of the difference," said Christopher Dye, WHO's coordinator of TB monitoring and evaluation, who was not involved in the study. "Because of the interaction between these two causes of illness and death that this paper reveals, then potentially we have a more powerful tool for controlling tuberculosis."
Dye also said scientists need to investigate whether TB drugs work as well on smokers as on nonsmokers.
About 1 billion people worldwide are carrying live tuberculosis infection in their lungs. Smoking increases the danger that any TB infection in the lungs will get out of control and cause TB symptoms, which can be fatal, said one investigator, Sir Richard Peto, professor of medical statistics at Oxford University.
The study compared the smoking habits of 43,000 men who died of various diseases in the late 1990s in the state of Tamil Nadu, southern India, with the habits of 35,000 men who were still living in the same region. Few women in the region smoke, so the study was conducted solely on men.
Results were similar in men who smoked cigarettes or "bidis," local cigarettes made from rolling tobacco in the leaf of another plant.
"Our study indicates that in rural India, about 12 percent of smokers, but only 3 percent of nonsmokers, will die prematurely from TB," Peto said.
The TB death risks for urban areas were 8 percent for smokers, compared with 2 percent for nonsmokers.
There were 4,000 deaths from TB in the study. If smokers had the same low risk as nonsmokers, there would have been fewer than 2,000 TB deaths, Peto said.
"It is a very important study. ... However, we have not yet taken serious measures to bring smoking under control, though all over the world smoking has been controlled tremendously," said Dr. Sanjiv Malik, secretary-general of the Indian Medical Association.
"We are the global capital of tuberculosis and in spite of the various TB control programs, we haven't been able to bring it down," Malik said. "Smoking incidence remains very high, especially in rural areas."
The Tobacco Manufacturers Association, a London-based trade group, said it does not comment on smoking and health issues.
Philip Morris International, which makes many cigarette brands, declined to comment specifically on the research, but spokesman Marc Fritsch said the company is "absolutely in line with what the overwhelming majority of the scientific community has to say" on the health effects of smoking.