Cohort study of all-cause mortality among tobacco users in Mumbai, India

Overall mortality rates are higher among cigarette smokers than non-smokers. However, very little is known about the health effects of other forms of tobacco use widely prevalent in India, such as bidi smoking and various forms of smokeless tobacco (e.g. chewing betel-quid). We therefore carried out a cohort study in the city of Mumbai, India, to estimate the relative risks for all-cause mortality among various kinds of tobacco users.

A baseline survey of all individuals aged > or = 35 years using voters' lists as a selection frame was conducted using a house-to-house approach and face-to-face interviews.

Active follow-up of 52,568 individuals in the cohort was undertaken 5-6 years after the baseline study, and 97.6% were traced. A total of 4358 deaths were recorded among these individuals. The annual age-adjusted mortality rates were 18.4 per 1000 for men and 12.4 per 1000 for women. For men the mortality rates for smokers were higher than those of non-users of tobacco across all age groups, with the difference being greater for lower age groups (35-54 years). The relative risk was 1.39 for cigarette smokers and 1.78 for bidi smokers, with an apparent dose-response relationship for frequency of smoking. Women were basically smokeless tobacco users, with the relative risk among such users being 1.35 and a suggestion of a dose-response relationship.

These findings establish bidi smoking as no less hazardous than cigarette smoking and indicate that smokeless tobacco use may also cause higher mortality. Further studies should be carried out to obtain cause-specific mortality rates and relative risks.