Incidence rate of oral lichen planus among Indian villagers.

In a house-to-house survey in South India, comprising 10,000 villagers, the age-adjusted incidence rate per 1,000 person-years for oral lichen planus was found to be 2.1 for males and 2.5 for females, based upon a 10-year follow-up study. The highest incidence was in the age group 55-64 for males and 45-54 for females. The age-adjusted relative risk was higher for the 'chewing habits' group (6.2) than for the 'smoking habit' group (2.2). The combined effect of the two habits appeared to be multiplicative; the age-adjusted relative risk for the mixed habit group being 13.7.