Risk factors for oral cancer in Brazil: a case-control study

Abstract

A case-control study of risk factors for carcinomas of the tongue, gum, floor, and other specified parts of the mouth was conducted in 3 metropolitan areas in Brazil: São Paulo (southeast), Curitiba (south), and Goiânia (central-west). We analyzed information on demographics, occupational history, environmental exposures, tobacco smoking and alcohol drinking habits, as well as diet, oral and other health characteristics obtained from interviews with 232 cases and 464 hospital non-cancer controls matched for 5-year age-group, sex, hospital catchment area and trimester of admission. Tobacco and alcohol consumption were the strongest risk factors irrespective of the anatomical site. The adjusted relative risks (RR) for ever vs. never smokers were: 6.3, 13.9, and 7.0, for industrial-brand cigarettes, pipe, and hand-rolled cigarettes, respectively. A strong correlation was seen between number of pack-years and risk. The RR for the heaviest vs. the lowest consumption categories (greater than 100 vs. less than 1 pack-years) was 14.8. Risk levels generally decreased to those of never smokers after 10 years had elapsed since stopping smoking. The risk associated with alcohol was mostly evident for wine (cancer of the tongue) and "cachaça" (all sites), a hard liquor distilled from sugar cane. Other important risk factors were drinking "chimarrão" (a type of maté), use of a wood stove for cooking, and frequent consumption of charcoal-grilled meat and manioc. Oral hygiene characteristics represented correlates of disease risk. A significant protective effect was observed for consumption of carotene-rich vegetables and citric fruits, but not for green vegetables in general.