Table 1. Basic information of the studies included in the meta-analysis.

First author [reference]	Year	Region	Ethnicity	NOS	AA/AG/GG (control)	χ2	PHWE	AA/AG/GG (case)	Methods
Killestein [18]	2000	Netherlands	Caucasian	5	40/43/23	2.97	0.09	42/68/35	NR
Li [20]	2008	China	Asian	8	35/17/3	0.24	0.63	29/16/6	PCR-LDR
Luomala [21]	1999	Finland	Caucasian	7	27/59/25	0.45	0.50	34/45/25	PCR-RFLP
Marrosu [22]	2000	Sardinia	Caucasian	8	44/59/23	0.17	0.68	49/75/33	PCR
Mousavi [23]	2007	Iran	Asian	7	34/80/42	0.13	0.72	45/75/37	PCR
Mycko [24]	1998	Poland	Caucasian	6	23/20/25	11.50	<0.05	42/23/14	PCR
Nejentsev [19]	2003	Finland	Caucasian	6	146/302/125	1.77	0.18	92/119/66	PCR-RFLP
		Spain	Caucasian	6	33/47/33	3.19	0.07	49/55/36	PCR-RFLP
Qiu [25]	2013	Australia	Caucasian	7	318/678*	–	>0.05	240/460*	TaqMan
Sanadgol [26]	2011	Iran	Asian	7	69/36/18	10.57	<0.05	49/24/5	PCR-SSP
Shawkatova [27]	2017	Slovakia	Caucasian	8	68/101/39	0.02	0.89	75/133/40	PCR-RFLP

Abbreviations: HWE, Hardy–Weinberg equilibrium; LDR, ligase detection reaction; NOS, Newcastle–Ottawa Scale; NR, not reported; PCR, polymerase chain reaction; RFLP, restriction fragment length polymorphism; SSP, sequence-specific primers; *, the allelic frequency data of A/G; –, no data.