Tobacco Chewing and Adult Mortality: a Case-control Analysis of 22,000 Cases and 429,000 Controls, Never Smoking Tobacco and Never Drinking Alcohol, in South India

Background: Tobacco is consumed in both smoking and smokeless forms in India. About 35-40% of tobacco consumption in India is in the latter. The study objective was to describe the association between chewing tobacco and adult mortality. Materials and Methods: A case-control study was conducted in urban (Chennai city) and rural (Villupuram district) areas in Tamil Nadu state in South India. Interviewed in 1998-2000 about 80,000 families (48,000 urban and 32,000 rural) with members who had died during 1995-1998. These were the cases and their probable underlying cause of death was arrived at by verbal autopsy. Controls were 600,000 (500,000 urban, 100,000 rural) individuals from a survey conducted during 1998-2001 in the same two study areas from where cases were included. Results: Mortality analyses were restricted to non-smoking non-drinkers aged 35-69. The age, sex, education and study area adjusted mortality odds ratio was 30% higher (RR:1.3, 95%CI:1.2-1.4) in ever tobacco chewers compared to never chewers and was significant for deaths from respiratory diseases combined (RR:1.5, 95%CI:1.4-1.7), respiratory tuberculosis (RR:1.7, 95%CI:1.5-1.9), cancers all sites combined (RR:1.5, 95%CI:1.4-1.7) and stroke (RR:1.4, 95%CI:1.2-1.6). Of the cancers, the adjusted mortality odds ratio was significant for upper aero-digestive, stomach and cervical cancers. Chewing tobacco caused 7.1% of deaths from all medical causes. Conclusions: The present study is the first large study in India analysing non-smoking non-drinkers. Statistically significant excess risks were found among ever tobacco chewers for respiratory diseases combined, respiratory tuberculosis, stroke and cancer (all sites combined) compared to never tobacco chewers.