OBJECTIVE: To study the effect of cessation of tobacco use on the incidence of lichen planus, leukoplakia and other oral mucosal lesions.
DESIGN: A 10–yr cohort study in a rural population of Ernakulam district, Kerala, India.
MATERIAL AND METHODS: Some 12 212 tobacco users were interviewed and examined in a basetine survey and re-examined annually for 10 years. At each examination they were exposed to health educational programs to encourage them to quit their tobacco use. The incidence rates were calculated using person-years method among those who stopped their tobacco use and all others.
RESULTS: A total of 77 681 person-years of observation accrued among men and 32 544 among women. Among men 6.5% of these and among women 14.4% were in the stopped category. The incidence of oral lichen planus did not show any consistent association with cessation of tobacco habits (incidence ratio I.35) but for leukoplakia there was a substantial drop in the incidence after cessation (incidence ratio 0.3I). Several other tobacco-associated oral mucosal lesions such as oral lichen planus-like lesion, smoker's palate, preteukoplakia, central papillary atrophy of the tongue and leukoedema showed either zero, or very small incidence, after cessation. CONCLUSION: The reported association between tobacco use and lichen planus appears to be indirect but for all other lesions it is direct. The cessation of tobacco use led to a substantial fall in the incidence of leukoplakia and other lesions implying a reduced risk for oral cancer after cessation of tobacco use.