The association between tea drinking and risk of head and neck cancer stratified by the use of alcohol, betel quid, or cigarette.

Abbreviations: CI = confidence interval; OR = odds ratio a.OR and 95% CI were calculated using unconditional logistic regression, adjusted for sex, age, education, cigarette smoking (pack-year categories), betel quid chewing (pack-year categories), and alcohol drinking (frequency) b.For never and occasional tea drinkers, the cup of tea per day = 0 and the cup-year of tea = 0. c.1 cup-year = 1 cup of tea per day ×1 year d.Years of consumption was cut off at the median e.Tests for interaction were performed using only two strata (Never and former+current).