. 2014 Jul 21;9(7):e102443. doi: 10.1371/journal.pone.0102443

Table 1. Main characteristics of the 29 studies for meta-analysis.

Number	Author	Year	Region	Total number of study	Male (%)	Genotypic distribution						Allele frequencies				HWE
						CC		CT		TT		C		T
						case	control	case	control	case	control	case	control	case	control
1	Sun, Liang^a	2013	Beijing	549	51.37	180	30	243	42	48	6	603	102	339	54	Yes
2	Mei, Qingbu	2012	Heilongjiang	215	No	17	17	51	70	23	37	85	104	97	144	Yes
3	Dai, Hongshuang^a	2012	Heilongjiang	180	55.00	51	31	54	27	15	2	156	89	84	31	Yes
4	Chen, Airong	2010	Gansu	219	59.62	57	34	74	17	33	4	188	85	128	25	Yes
5	Zhang, Qiaohui^a,b,c	2009	Shanxi	278	60.79	66	26	94	17	66	9	226	69	226	35	Yes
6	Qiu, Yi^a,b	2009	Zhejiang	299	54.85	83	53	68	29	48	18	234	135	164	65	No
7	Hu, Ling^a,b	2009	Shanxi	211	62.56	47	26	63	17	49	9	157	69	163	35	Yes
8	Wen, Jie	2008	Shanghai	211	52.13	43	27	82	25	29	5	168	79	140	35	Yes
9	Luo, Dan^a,b	2008	Beijing	226	47.79	59	43	63	31	19	11	181	117	101	53	Yes
10	Chen, Ping	2008	Heilongjiang	240	No	19	14	70	73	27	37	108	101	124	147	No
11	Zhang, Chunyu^a,b,c	2007	Neimenggu	141	51.77	28	34	29	19	19	12	85	87	67	43	No
12	Luo, Dan^a,b	2007	Beijing	274	52.64	55	42	102	35	26	14	222	119	154	63	Yes
13	Yue, Hong^a,b,c	2006	Shanxi	282	57.09	66	17	131	11	55	2	263	45	241	15	Yes
14	Xiao, Yan^a,b	2006	Guizhou	146	No	16	47	53	25	4	1	85	119	61	27	Yes
15	Sun, Ying^a,b,c	2006	Tianjin	355	60	113	47	85	25	68	17	311	119	221	49	No
16	Shi, Chengjun	2006	Guangdong	295	No	108	68	60	34	18	7	276	170	96	48	Yes
17	Liang, Wenchang	2005	Zhejiang	122	No	33	17	34	18	15	5	100	52	64	28	Yes
18	Guo, Lixin^a,b	2005	Beijing	288	57.29	60	58	51	34	50	35	171	150	151	104	No
19	Sun, Jiazhong.	2005	Hubei	342	67.25	101	63	78	31	49	20	280	57	176	71	No
20	Zhou, Jun^a,b,c	2004	Heilongjiang	208	No	16	8	78	31	45	30	110	47	168	91	Yes
21	Sun, Lei^a,b,c	2004	Shandong	155	47.44	27	29	52	18	27	2	106	76	106	24	Yes
22	Mao, Li^a,b,c	2004	Jiangsu	122	46.92	35	18	37	18	11	3	107	70	59	24	Yes
23	Chen, Airong^a,b,c	2004	Gansu	126	64.29	24	21	45	9	22	5	93	51	89	19	No
24	Xu, Jinsheng^a,b,c	2003	Hebei	175	45.14	30	7	54	25	39	20	114	39	132	65	Yes
25	Zhang, Guodong	2002	Shanghai	298	No	56	40	108	49	34	11	220	129	176	71	Yes
26	Shi, Jieping	2002	Jilin	106	No	12	22	31	29	7	5	55	55	45	45	Yes
27	Yang, Guoqing^a,c	2001	Beijing	288	53.61	57	26	113	28	56	8	227	80	225	44	Yes
28	Wang, Longqing^a	2001	Guangdong	264	52.27	65	37	75	38	39	10	205	112	153	58	Yes
29	Hu, Sheng^a,b,c	2001	Hubei	168	55.36	49	30	48	24	16	1	146	84	80	26	Yes

HWE: Hardy-Weinbery equilibrium; a: The distribution of gender between case and control group is in balance; b: The distribution of age between case and control group is in balance; c: The distribution of BMI between case and control group is in balance.