Influence of cigarette filters on the risk of developing oral leukoplakia in a Kenyan population.

OBJECTIVE To determine the influence of cigarette filters and the effect of smoking Kiraiku (home processed, hand rolled tobacco) on the risk of developing oral leukoplakia among cigarette smokers. DESIGN Case control using population-based study groups in a Kenyan rural community. MATERIALS AND METHODS 85 cases and 141 controls identified in a cross-section house-to-house screening of subjects aged 15 years and over and matched for sex, age (+/- 3 years) and cluster origin were compared for their use of filter and non-filter cigarettes as well as their history of smoking Kiraiku. RESULTS The relative risk (RR) of oral leukoplakia was 9.1 (95% confidence intervals (CI) = 4.1-20.2) in smokers of filter cigarettes and 9.8 (95% CI = 2.3-47.0) in smokers of non-filter cigarettes. The RR in the latter compared to the former was 1.1 and was not statistically significant. Regarding the influence of smoking Kiraiku, the RR of this lesion was 29.3 in smokers of both Kiraiku and filter cigarettes and 17.3 in smokers of both Kiraiku and non-filter cigarettes. CONCLUSIONS There was no statistically significant difference between the influence of filter and non-filter cigarettes on the risk of developing oral leukoplakia. The effect of Kiraiku on the risk of this lesion was stronger in filter than in non-filter cigarettes. However, the confounding effect of tobacco dose response parameters could not be ruled out.