A study of dose-response relationship between tobacco habits and oral leukoplakia.

In a house-to-house survey in Ernakulam district, Kerala, India, 12,213 tobacco users were interviewed about the details of their tobacco usage and examined for the presence of leukoplakia. The frequency of tobacco habit was associated with the prevalence of leukoplakia indicating a positive dose-response relationship. The dose-response relationship remained significant, taking age, sex, and the type of tobacco habit into account. After adjusting for all these variables jointly the association still remained significant. The dose-response relationship was stronger for the smoking habit than for the chewing habit. A weaker relationship in the chewing habit was not due to the duration of chewing habit or the habit of retaining the betel quid in the mouth while sleeping. Thus the dose-response relationship, although significant, was different for tobacco smoking and chewing habits.