Most adult deaths in India involve vascular disease, pulmonary tuberculosis or other respiratory diseases. In the first major study of how smoking causes death in India, Vendhan Gajalakshmi from Chennai’s Epidemiology Research Centre and her colleagues compared the tobacco smoking of 43,000 men (from both urban and rural areas) who had died of various diseases in the late 1990s with that of 35,000 living men (the control group).

In the urban study area, the death rate from medical causes of regular smokers was double that of those who had never smoked. The risks were substantial both for cigarette smoking (the main urban habit) and for bidi smoking. Of this excess mortality among smokers, most involved respiratory diseases (chiefly tuberculosis) or vascular diseases (chiefly heart attack). Smoking also caused similar excesses of respiratory and vascular mortality in the rural study area.

Vendhan Gajalakshmi commented: "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. Half the extra TB deaths were between the ages of 25 and 54. In all, about a quarter of all smokers are killed by smoking at ages 25-69—those killed at these ages lose 20 years of life on an average."

Co-author Richard Peto from the University of Oxford, U. K., adds: "About a billion people worldwide are carrying live tuberculosis infection in their lungs, but if they do not smoke then most will never become seriously ill from TB. 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. 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 per cent of smokers (but only three per cent of non-smokers) will die prematurely from TB. In urban India the corresponding risks are eight per cent and two per cent."