Tea consumption and its interactions with tobacco smoking and alcohol drinking on oral cancer in southeast China.

BACKGROUND/OBJECTIVES: Epidemiological results on the association between tea consumption and oral cancer remain controversial. We aimed to evaluate the exact relationship between tea consumption and oral cancer in Chinese population. SUBJECTS/METHODS: A large-scale case-control study was conducted on 586 oral cancer patients and 1024 controls frequency-matched by age and gender. Epidemiological data were collected through face-to-face interviews with a structure questionnaire. Unconditional logistic regression model was used to assess the effect of tea consumption on oral cancer stratified by smoking, alcohol drinking and demographics. Quantity of tea consumed (ml/day) was categorized into five subgroups based on quartiles and then its interactions was evaluated with tobacco smoking and alcohol drinking at each subgroup. RESULTS: Tea consumption showed an inverse association with oral cancer for non-smokers or non-alcohol drinkers (the odds ratios (ORs) were 0.610 (95% confidence interval (CI): 0.425-0.876) and 0.686 (95% CI: 0.503-0.934), respectively). For smokers or alcohol drinkers, decreased risk was only observed in those who consumed >800 ml/day. Furthermore, oolong tea consumption was associated with decreased risk of oral cancer in smokers or alcohol drinkers but not in non-smokers or non-alcohol drinkers. Tea consumption combined with smoking or/and alcohol drinking had a greater risk than tea consumption alone, but the risk was roughly reduced from zero to Q4 (>800 ml/day). Additionally, when stratified by demographics, the protective effect of tea was especially evident in females, urban residents, normal body mass index population (18.5-23.9), farmers, office workers and those aged <60 years. CONCLUSIONS: Tea consumption protects against oral cancer in non-smokers or non-alcohol drinkers, but this effect may be obscured in smokers or alcohol drinkers. Additionally, demographics may modify the association between tea consumption and oral cancer.

[Tea, coffee intakes and risk of oral squamous cell carcinoma: a case-control study].

Objective: To evaluate the effects of tea and coffee intakes on oral squamous cell carcinoma (OSCC) stratified by milk intake. Methods: A case-control study involving 593 OSCC patients confirmed by pathological diagnoses and 1 128 gender-age frequency matched controls was conducted in Fujian province during September 2010-March 2016. Unconditional logistic regression was used to calculate adjusted odds ratios (aORs) and corresponding 95% confidence intervals (CIs) to assess the effects of coffee, tea intakes and related variables on OSCC. Additive interaction was estimated by relative excess risk interaction (RERI), attributable proportions interaction (API) and synergy index (SI). Results: Tea intake was significantly associated with decreased risk of OSCC: the adjusted ORs were 0.54 for all subjects (95%CI: 0.41-0.71), 0.47 for milk consumers (95%CI: 0.31-0.71) and 0.57 for non-milk consumers (95%CI: 0.40-0.81). Moreover, starting tea drinking at age ≥25 years, moderate tea concentration and water temperature, drinking green tea and oolong tea showed effects to decrease the risk for OSCC in three groups. Additionally, there was a tendency of a reduced risk with increased daily tea drinking and longer tea-drinking period (all trend P<0.05). No significant association was observed between coffee intake and OSCC. A multiplicative but not additive interactions was found between tea drinking and milk intake. Additionally, we did not observe multiplicative and additive interaction between coffee drinking and milk intake. Conclusion: Tea drinking is a protective factor for OSCC, and there is a multiplicative interaction between tea drinking and milk intake. Therefore, tea drinking and increasing intake of milk can reduce the risk of OSCC at certain extent.