Table 1.

Baseline characteristics of the cases and controls of included studies

Study	nS	Mean age (year)	nM/nF	nG			Allele frequency
				B1B1	B1B2	B2B2	B1	B2
Li et al., 2007
Case	176	61.7±12.5 a		82	73	21	0.588	0.412
Control	40	55.8±13.1		15	19	6	0.584	0.416
Qin et al., 2004
Case	249	58.8±8.9	169/80	81	131	37	0.588	0.412
Control	167	55.1±9.0	89/78	49	97	21	0.584	0.416
Wang et al., 2004
Case	128	62.9±5.6	82/46	50	66	12	0.648	0.352
Control	247	59.5±8.4	142/105	72	123	52	0.540	0.460
Wang, 2006
Case	123	62.36b	44/59	38	65	20	0.568	0.432
Control	103	48.17	84/39	33	51	19	0.573	0.427
Wu et al., 2001
Case	149	20–82c		45	79	25	0.595	0.405
Control	274	28–83		63	159	52	0.584	0.416
Yan et al., 2004
Case	106	60±9	81/25	41	46	19	0.604	0.396
Control	64	57±11	31/33	19	34	11	0.564	0.437
Zhang G. et al., 2005
Case	88	65±10		31	40	17	0.580	0.420
Control	94	54±18		32	50	12	0.606	0.394
Zhang Y. et al., 2003
Case	234	59.5±8.2	135/99	76	126	32	0.595	0.405
Control	164	58.2±9.3	98/66	49	95	20	0.588	0.412
Zhao et al., 2004
Case	238	61.3±9.2	224/217	95	105	38	0.620	0.380
Control	203			60	109	34	0.564	0.436
Zheng et al., 2004
Case	203	59.3±8.7	137/77	66	114	23	0.606	0.394
Control	100	58.4±6.5	66/34	33	55	12	0.605	0.395

n _S: number of samples; n _M/n _F: male number/female number; n _G: number of genotype

^aMean age is expressed as mean±SD

^bMean age is expressed as mean

^cMean age is expressed as range