Table 1.

Main characteristic of the included studies

First author	Year	Country	Age	Patients			Clinical stage	Duration of follow-up
				Total	Cases	Controls
Feugier	2005	Belgium	60-75	399	202	197	I-IV	60
Wang YH	2006	China	24-78	48	26	22	I-IV	24
Aviles-a	2007	Mexico	65-85	204	101	103	IV	60
Aviles-b	2007	Mexico	25-65	196	98	98	III-IV	53.4
Jia XL	2011	China	23-76	36	18	18	II-IV	26 (12-48)
Yang SL	2011	China	18-78	49	23	26	I-IV	35 (4-66)
Jin H	2012	China	19-78	43	25	18	I-IV	12-36
Liu J	2012	China	19-82	116	52	64	I-IV	12-36
Xu SF	2013	China	14-74	73	39	34	I-IV	28 (6-59)
Zeng AP	2013	China	29-69	48	24	24	I-IV	36