Zheng 1993.

Study characteristics
Methods	HCC in China
Participants	Participants: 404 (male/female: NR) cases and 404 (male/female: NR) controls Inclusion criteria: aged 18‐80 years, newly diagnosed oral cancer in residents in Beijing, China. Recruitment: from 1 May 1989‐24 December 1989
Interventions	N/A
Outcomes	Number of cases Oral cancer: 404 (male/female: NR) cases
Green tea in exposure categories	Exposure assessment: intake of green tea Lowest exposure: < 1 cup/month Highest exposure: ≥ 1 cup/month
Notes	Funding: not declared Statistical methods: conditional logistic regression Variables controlled in analysis: sex, age, tobacco smoking, alcohol drinking, inadequate dentition, years of education and Quetelet Index Variables controlled by matching: sex and age (± 5 years)