Table 1. Characteristics of studies included in the meta-analysis.

First author	Year	Country	Ethnicity	Cancer types	Source of controls	Sample size
						Case	Control
Coutelle	1997	France	European	UADT	HB	39	37
Harty	1997	Puerto Rico	Mixed	UADT	PB	146	146
Freudenheim	1999	USA	European	Breast	PB	315	356
Bouchardy	2000	France	European	UADT	HB	244	167
Chao	2000	China	Asian	UADT	HB	88	434
Olshan	2001	USA	European and African	UADT	HB	173	194
Sturgis	2001	USA	European	UADT	HB	229	575
Schwartz	2001	USA	European	UADT	PB	333	541
Dijk	2001	Netherlands	European	Bladder	HB	115	131
Zavras	2002	Greece	European	UADT	HB	93	99
Yokoyama	2002	Japan	Asian	UADT	PB	234	634
Freudenheim	2003	USA	Mixed	Lung	PB	113	212
Nishimoto	2004	Brazil	Mixed	UADT	Combined	141	134
Coutelle	2004	German	European	Breast	HB	117	111
Peters	2005	USA	European	UADT	PB	521	599
Wang	2005	USA	European	UADT	HB	348	330
Homann	2006.	German	European	UADT and Hepatocellular	Combined	293	729
Logt	2006	Netherlands	European	Colorectal	PB	320	385
Terry	2006	USA	Mixed	Breast	PB	1047	1101
Terry	2007	USA	Mixed	UADT	PB	197	160
Zhang	2007	Poland	European	UADT	PB	297	425
Yin	2007	Japan	Asian	Colorectal	PB	685	777
Visvanathan	2007	USA	European	Breast	PB	303	312
Asakage	2007	Japan	Asian	UADT	HB	96	642
Curtin	2007	USA	Mixed	Colorectal	PB	915	1969
Solomon	2008	India	Mixed	UADT	HB	126	100
Hashibe	2008	Multi-Countries	European and Mixed	UADT	Combined	3393	4851
Li	2008	South Africa	African and Mixed	UADT	PB	237	268
Oze	2009	Japan	Asian	UADT	HB	585	1170
Garcia	2010	Brazil	Mixed	UADT	HB	207	244
Duchonova	2010	Czech	European	Pancreatic	HB	235	264
Kortunay	2010	Turkey	European	UADT	HB	50	100
Soucek	2010	Slav	European	UADT	HB	121	121
Brocic	2011	Serbia	European	UADT	Combined	123	177
Mckay	2011	Multi-Countries	European	UADT	Combined	6675	8024

UADT, upper aerodigestive tract; HB, hospital based; PB, population based; Combined, studies conducted on both population-based and hospital-based control group.