Smoking causes half the tuberculosis deaths in Indian men

August 14, 2003

Half the male tuberculosis deaths in India are caused by smoking, and three quarters of the smokers who become ill with tuberculosis (TB) would not have done so if they had not smoked. These are the conclusions of a major new study led by the Epidemiological Research Center in Chennai, India and primarily funded by the UK Medical Research Council and Cancer Research UK.

The study found that in India male smokers are about four times as likely to become ill with TB as non-smokers, and consequently four times as likely to die from the disease.

The study also showed the smokers had higher death rates from heart disease and from various types of cancer.

In total, about a quarter of the smokers studied were killed at ages 25-69 by their habit, those killed at these ages losing, on average, 20 years of life.

This is the first major study to be completed on 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. More than 4000 of these deaths were from TB, but if the smokers had had the same low risks as non-smokers there would have been fewer than 2000 TB deaths. Few women in south India smoke, so the study was only of men.

Dr Vendhan Gajalakshmi of the Epidemiological Research Center in Chennai, India, led the research. She said: "Smoking causes half the male tuberculosis deaths in India. Almost 200,000 people a year in India die from tuberculosis because they smoked, and half the smokers killed by TB are still only in their thirties, forties or early fifties when they die."

Co-investigator, Sir Richard Peto, professor of medical statistics at the University of Oxford, UK, said: "In some parts of the world the main way smoking kills people is by damaging the lung's defences against chronic TB infection. Our study indicates that in rural India about 12% of smokers, but only 3% of non-smokers, die prematurely from TB."

Co-investigator Dr Prabhat Jha, of the University of Toronto, said: "Not only in Asia and Africa, but also throughout America and Europe, smoking will increase the number of people who develop clinical TB themselves and who can then infect others, unless properly treated and cured."

About a billion people worldwide are carrying live TB infection in their lungs, but if they do not smoke then most will never become seriously ill from it. Smoking increases the danger that any TB infection already in the lungs will get out of control and cause clinical TB, which can kill and can easily be spread to other people.

Tuberculosis 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, and in some countries it is now becoming more common.
-end-
The study is published 16 August in The Lancet medical journal. The full paper can be accessed at: http://www.ctsu.ox.ac.uk/projects/IndiaTB

Contacts:

Asia
Dr Vendhan Gajalakshmi
Epidemiological Research Center, Chennai
Office (tel/fax): 91-44-2644-6030
Cell: 91-98-4016-0050
Email: gajaerc@rediffmail.com

Europe
Professor Sir Richard Peto
Nuffield Department of Clinical Medicine
University of Oxford, UK
Office: 44-1865-404-801
Cell: 44-7771-960-329
Email: secretary@ctsu.ox.ac.uk

Press Office
Medical Research Council
Office: 44-20-7637-6011
E-mail: press.office@headoffice.mrc.ac.uk

North America
Dr Prabhat Jha
Centre for Global Health Research
University of Toronto, Canada
Office: 1-416-864-6042
Cell: 1-416-839-0332
Email: Prabhat.jha@utoronto.ca

Jessica Whiteside
University of Toronto Public Affairs
Office: 1-416-978-5948
Email: Jessica.whiteside@utoronto.ca

NOTES TO EDITORS: Lay Summary of Key Findings

University of Toronto

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