Table 1.

Characteristics of studies included in the meta-analysis.

							Sample size		Mean age (years)		Genotype		Allele (M/m)∗			OR (95% CI)
SNPs	Author and reference	Year	Country	Ethnicity	Case	Control	Case	Control	Case	Control	Case	Control	Dominant model	Allelic model	NOS	HWE
rs4784227	Yao Sun	2020	China	Asian	503	503	52.04 ± 9.52	51.90 ± 9.55	266/199/38	292/180/31	275/731	242/764	1.23 (0.96–1.58)	1.19 (0.97–1.45)	6	0.644135
(C > T)	Nehle Jamali	2020	Iran	Asian	107	91	53.51 ± 5.16	52.51 ± 5.97	31/46/30	36/49/6	106/108	61/121	1.61 (0.89–2.90)	1.95 (1.30–2.93)	7	0.046983
	Xiaoxiao Zuo	2020	China	Asian	681	680	50.58 ± 9.84	50.63 ± 9.71	353/270/52	394/240/41	374/976	322/1028	1.28 (1.03–1.59)	1.22 (1.03–1.45)	6	0.581859
	Amir Tajbakhsh	2019	Iran	Asian	505	567	50.52 ± 12.29	43.45 ± 12.21	209/218/78	285/222/60	374/636	342/792	0.52 (0.42–0.66)	1.49 (1.26–1.77)	6	0.092861
	Zhiping Deng	2016	China	Asian	551	577	49.09 ± 11.022	48.790 ± 8.294	123/102/13	340/205/36	128/348	277/885	1.38 (1.02–1.86)	1.19 (0.98–1.44)	6	0.495311
	Yuxiang Lin	2014	China	Asian	702	794	47.8 ± 10.9	48.7 ± 9.7	331/302/68	424/313/57	438/964	427/1161	1.27 (1.03–1.56)	1.24 (1.06–1.45)	7	0.941233
	Ali Hajizadeh	2017	Iranian	Asian	126	160	–	–	75/35/16	54/96/10	67/185	116/204	0.22 (0.095–0.549)	–	6	0.000162
	Furu Wang	2020	China	Asian	1006	1017	51.59 ± 11.14	51.54 ± 11.18	500/415/83	569/385/61	581/1415	507/1523	1.27 (1.06–1.52)	–	7	0.69847

^∗M/m: major/minor allele

Genotype presented as wild type/heterozygous/homozygous; −, not available; SNP = single nucleotide polymorphisms, OR = odds ratio, 95% CI = 95% confidence interval, NOS = Newcastle–Ottawa quality assessment scale, HWE = Hardy–Weinberg equilibrium.