[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.