UNLABELLEDOBJECTIVE To investigate the effect of tea on oral cancer in nonsmokers and nondrinkers.

METHODSA case-control study were performed between September 2010 and January 2015 including 203 oral cancer cases in nonsmokers and nondrinkers with pathologically confirmed and 572 community controls. The related information included socio-demographic characteristics, detailed information on tobacco smoking and alcohol and tea consumption, personal medical history, family history of cancer, and occupational history were collected from all subjects. Unconditional logistic regression analysis was used to calculate the odds ratios (OR) and 95% confidence intervals (95% CI) to examine the effect of tea on oral cancer and to assess multiplicative interactions between tea and passive smoking. We also stratified by age, sex, residence, and passive smoking to explore possible difference in association between subgroups. Additive interactions between tea and passive smoking were assessed using relative excess risk due to interaction (RERI), attributable proportion (AP), and synergy index (SI).

RESULTSCompared with non-tea drinkers, tea consumption (OR = 0.52, 95% CI: 0.34-0.81), age of tea drinking initiation (years) ≥ 18 (OR = 0.54, 95% CI: 0.34-0.85), duration of tea consumption (years) < 20 (OR = 0.49, 95% CI: 0.27-0.90), duration of tea consumption (years) ≥ 20 (OR = 0.55, 95% CI: 0.32-0.95), average daily tea consumed < 700 ml (OR = 0.52, 95% CI: 0.32-0.86), moderate concentration of tea consumed (OR = 0.56, 95% CI: 0.32-0.96), weak concentration of tea consumed (OR = 0.35, 95% CI: 0.16-0.77), drinking green-tea (OR = 0.48, 95% CI: 0.28-0.82) and drinking moderate temperature of tea (OR = 0.55, 95% CI: 0.31-0.98) could reduce the risk of oral cancer; Stratified analysis indicated the protective effects of tea drinking on female (OR = 0.53, 95% CI: 0.30-0.94), age < 60 years old (OR = 0.53, 95% CI: 0.29-0.97), live in the urban (OR = 0.38, 95% CI: 0.20-0.69) and no passive smoking (OR = 0.47, 95% CI: 0.25-0.86) population with nonsmoking and nondrinking was more obvious; Crossover analysis showed tea and passive smoking did not exist multiplication interaction relationship (OR = 0.95, 95% CI: 0.41-2.20) and addition interaction relationship (RERI = -0.15, 95% CI: -0.92-0.62;AP = -0.16, 95% CI: -1.06-0.73; SI = -0.18, 95% CI: -1.44-0.87).

CONCLUSIONTea consumption, age of tea drinking initiation, duration of tea consumption, average daily tea consumed, concentration of tea consumed, types of tea and temperature of tea might have impact on the incidence of oral cancer in nonsmokers and nondrinkers to a certain extent.