INFLUENCE OF DOSE AND CESSATION OF KIRAIKU, CIGARETTES AND ALCOHOL-USE ON THE RISK OF DEVELOPING ORAL LEUKOPLAKIA

Data from a previously-reported study of oral leukoplakia-associated r isk factors in a Kenyan population were further analyzed to determine the influence of dose and cessation. Specifically, risk analysis was m ade with respect to kiraiku (a traditional Kenyan type of home-made, h and-rolled tobacco product), cigarettes, and commercial beer. The rela tive risk (RR) of oral leukoplakia among those who smoked >10 cigarett es was 14.7, as compared to 6.7 among those who smoked less than or eq ual to 10 cigarettes. With regard to duration, the RR increased from 7 .4 in those who had smoked for <less than or equal to>15 years to 10.8 in those who had smoked for greater than or equal to 30 years. Among those who had quit smoking, RR value was significant only in ex-kiraik u smokers (RR=4.9, 95% confidence interval (CI)=2.3-20.4) and was depe ndent on both the duration of smoking and duration since quitting. For commercial beer, the RR was significant in consumers of >10 bottles p er drinking day (RR=4.2, 95% CI=1.0-3.9) and in those whose who drank for greater than or equal to 5 days per month (RR=3.8, 95% CI=1.0-15.1 ). Duration of beer consumption did not significantly influence the RR of oral leukoplakia. The RR in ex-beer consumers was not statisticall y significant. These findings suggest a dose-dependent association bet ween oral leukoplakia and the use of tobacco and alcohol, in which the number of cigarettes smoked, the quantity of beer consumed, and the f requency of consumption were more important than the duration of use o f these products. Furthermore, while oral leukoplakia due to cigarette smoking may regress completely, those due to kiraiku may persist for more than 10 years after cessation of these habits.