Smoking a major cause of tuberculosis deaths in men in India: study
Friday, August 15, 2003
TORONTO (CP) - Smoking is the cause of half the male tuberculosis deaths in India, says a new study by an international team of researchers.
Smoking increases the probability of developing potentially fatal clinical TB, which can then easily infect other people. Almost 200,000 people a year in India die from TB because they smoke.
"Not only in Asia and Africa, but also in America and Europe, smoking will increase the number of people who develop clinical TB themselves and can then infect others, unless properly treated and cured," said one of the authors, Dr. Prabhat Jha, Canada Research Chair of Health and Development at the University of Toronto and director of the Centre for Global Health Research at St. Michael's Hospital.
He said TB still causes about 1.6 million deaths a year worldwide, including more than a million in Asia, 400,000 in Africa and 100,000 in the Americas and Europe.
The study, published in the British medical journal The Lancet, found that male smokers in India are about four times as likely to develop TB as their non-smoking countrymen and therefore four times as likely to die from TB.
"Half of the smokers killed by TB are still only in their 30s, 40s or early 50s when they die," said Dr. Vendhan Gajalakshmi of the Epidemiological Research Center in Chennai, India, who led the study.
This is the first major study of how smoking causes death in India. It compared the smoking habits of 43,000 men who had died of various diseases in the late 1990s with the habits of 35,000 living men. (Few women in South India smoke, so the study is of men.)
More than 4,000 of these deaths were from TB, but if smokers had the same low risks as non-smokers there would have been fewer than 2,000 TB deaths. Smokers also had higher death rates from heart disease and from various types of cancer: in total, about a quarter of all smokers are killed by their habit at ages 25-69. Those killed at these ages by tobacco lose an average of 20 years of life expectancy.
About a billion people worldwide are carrying live TB infection in their lungs, but if they don't smoke most will never become seriously ill. Smoking increases the danger that TB infection will get out of control and cause clinical TB, which can kill and can easily be spread to other people.
"In some parts of the world the main way smoking kills people is by damaging the lung's defences against chronic TB infection," said another author, Richard Peto, professor of medical statistics at the University of Oxford, England. "Our study indicates that in rural India about 12 per cent of smokers and three per cent of non-smokers die prematurely from TB."
The study, primarily funded by the UK Medical Research Council and Cancer Research, projected that by 2025 tobacco deaths in middle-aged men in India would reach one million.
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