Table 2

General characteristics of cohort studies used for meta-analysis

Study	Region	Period	Incidence rate	Cohort size	No. of cases	Years of follow-up	Endpoint	Quality score	Source of cohort	Adjusting factors
Chow et al 46	USA	1954–1980	Low	248 046	48	26	Mortality	6	Veterans	Age, calendar year
Friborg et al 10	Singapore	1993–2005	High	61 320	173	12	Morbidity	9	Population-based	Age, sex, dialect group, year of interview, education
Hsu et al 43	Taiwan	1984–2006	Moderate	9622	32	Mean 18.1	Incidence	9	Population-based	Age, two anti-EBV viral serum-markers
Lin et al 24	Guangzhou	1988–1999	High	101 823	34	Mean 7.3	Incidence	8	Factory workers and drivers	Age, sex, education, drinking status, occupation