Nass use, cigarette smoking, alcohol consumption and risk of oral and oesophageal precancer.

In a cross sectional study, conducted in Uzbekistan, an area with a high incidence of oral and oesophageal cancer, 1569 men were interviewed regarding use of nass quid, cigarette smoking and alcohol drinking. All subjects in the study had an oral examination, and oesophagoscopy was performed in 1344 men. Nass use and cigarette smoking emerged as independent risk factors for oral leukoplakia. The prevalence odds ratio (OR) for life-time nass intake equivalent rose from 1.0 in never-users to 5.17 [95% confidence interval (CI), 3.10-8.61] in the highest category; for total pack-years of cigarettes smoked the risk rose from 1.0 in never-smokers to 10.03 (95% CI, 4.9-20.6) in the highest category. There was a significant trend in risk (P < 0.001), for both factors. In the group with oral leukoplakia, the effect of nass use and cigarette smoking appeared to be additive. Cigarette smoking was also found to be an independent risk factor for oesophageal lesions and was significantly associated with chronic oesophagitis. The risk of chronic oesophagitis in the group with the highest pack-years of cigarettes smoked was approximately double that among non-smokers [Odds ratio (OR) = 2.47; 95% CI 1.34-4.56]. There was a weak association between nass use and oesophageal pathology: the highest life-time intake equivalent was associated with an OR of 1.56 (95% CI 1.09-2.23). Alcohol intake was not found to be independently associated with the presence of oral and oesophageal precancerous lesions.