Table 1. Characteristics of included studies selected for meta-analysis.

Study	Year	Country	Enthicity	Region	Sample size		Genotype distributions in cases/controls			Genotyping	Quality	HWE*
					Case	Control	11	12	22	method	score
rs2241766
Mohammadzadeh	2016	Iran	Caucasian	Western Asian	100	100	75/65	24/31	1/4	PCR-RFLP	8	0.899
Mofarrah	2016	Iran	Caucasian	Western Asian	152	72	82/56	35/13	35/3	PCR-HRM	8	0.072
Esteghamati	2012	Iran	Caucasian	Western Asian	114	127	48/68	41/46	25/13	PCR-RFLP	7	0.222
Nan	2012	China	Mongoloid	Eastern Asian	213	467	115/237	84/191	14/39	PCR-HRM	8	0.952
Al-Daghri	2011	Saudi Arabia	Caucasian	Western Asian	122	298	77/220	35/72	10/6	PCR-RFLP	7	0.969
Chiodini	2010	Italy	Caucasian	Southern Europe	499	503	321/359	168/126	10/18	Taqman	8	0.102
Ma	2008	China	Mongoloid	Eastern Asian	159	31	94/12	55/16	10/3	PCR-RFLP	8	0.479
Qi	2006	China	Mongoloid	Eastern Asian	266	672	204/529	62/143		Taqman	8	-
Qi	2005	China	Mongoloid	Eastern Asian	219	599	170/440	49/159		Taqman	8	-
Lacquemant Swiss	2004	Switzerland	Caucasian	Northern Europe	107	181	76/145	27/34	4/2	PCR	8	0.997
Lacquemant French	2004	Switzerland	Caucasian	Northern Europe	55	130	27/57	25/65	3/8	PCR	7	0.059
Bacci	2004	Italy	Caucasian	Southern Europe	130	211	90/140	35/60	5/11	PCR	8	0.182
rs1501299
Mohammadzadeh	2016	Iran	Caucasian	Western Asian	100	100	38/56	55/42	7/2	PCR-RFLP	9	0.063
Katakami	2012	Japan	Mongoloid	Eastern Asian	213	2637	129/1358	71/1047	13/232	PCR	8	0.139
Esteghamati	2012	Iran	Caucasian	Western Asian	114	127	76/63	30/47	8/17	PCR	8	0.095
Al-Daghri	2011	Saudi Arabia	Caucasian	Western Asian	123	297	47/111	57/142	19/44	PCR-RFLP	7	0.897
Chiodini	2010	Italy	Caucasian	Southern Europe	499	503	271/239	189/198	39/66	Taqman	8	0.016
Qi	2006	China	Mongoloid	Eastern Asian	280	684	159/374	104/258	17/52	Taqman	8	0.420
Qi	2005	China	Mongoloid	Eastern Asian	228	594	105/293	111/249	12/52	Taqman	8	0.930
Lacquemant Swiss	2004	Switzerland	Caucasian	Southern Europe	106	179	57/96	40/65	9/18	PCR	7	0.166
Lacquemant French	2004	Switzerland	Caucasian	Northern Europe	55	130	25/73	26/50	4/7	PCR	8	0.679
Bacci	2004	Italy	Caucasian	Southern Europe	142	234	70/118	65/83	7/28	PCR	7	0.031

For rs2241766 variant, 11, 12 and 22 represent TT, GT, GG, respectively; for rs1501299 variant, 11, 12 and 22 represent GG, TG and TT, respectively.

* P value for Hardy–Weinberg equilibrium test in controls