Table 8. Stratified meta-analysis of eligible cross-sectional studies by several study items related to study characteristics for the pooled odds ratio (OR) for type 2 diabetes mellitus (DM) per 1 increase in risk alleles carried in relation to single nucleotide polymorphism (SNP).

Item		Number of data	OR (95% CI)	Q statistics	I-squared	P value of heterogeneity	Meta-regression $
Total		40	1.16 (1.13–1.19)	613.3	93.6%	<0.001
Number of SNPs	<10	12	1.25 (1.11–1.31)	37.8	70.9%	<0.001
	≥10	28	1.14 (1.11–1.17)	522.1	94.8%	<0.001	0.002
Mean age	<55 years	16	1.17 (1.11–1.22)	191.4	92.2%	<0.001
	≥55 years	24	1.16 (1.13–1.20)	395.5	94.2%	<0.001	0.95
Proportion of men	<50%	26	1.14 (1.11–1.17)	361.5	93.1%	<0.001
	≥50%	13	1.21 (1.16–1.26)	101.6	88.2%	<0.001	0.04#
	N/A	1	1.13 (1.05–1.22)	—	—	—	—
Country	Western	24	1.13 (1.10–1.16)	307.0	92.5%	<0.001
	Non-Western	16	1.20 (1.16–1.25)	213.7	93.0%	<0.001	0.01
Dominant ethnic group	Asian	16	1.20 (1.16–1.25)	233.4	93.6%	<0.001
	Non-Asian	24	1.13 (1.10–1.16)	273.4	91.6%	<0.001	0.01
Mean BMI*	<27 kg/m2	22	1.19 (1.15–1.24)	448.4	95.3%	<0.001
	≥27 kg/m2	18	1.11 (1.09–1.14)	88.3	80.7%	<0.001	0.03
Adjustment for BMI	Yes	31	1.16 (1.13–1.20)	535.5	94.4%	<0.001
	No	9	1.15 (1.10–1.21)	66	87.9%	<0.001	0.82
Using OGTT to diagnose DM	Yes	14	1.19 (1.14–1.25)	205.1	93.7%	<0.001
	No	26	1.15 (1.11–1.18)	389.0	93.6%	<0.001	0.17
Excluding IGT from non-cases	Yes	7	1.28 (1.22–1.34)	15.4	31.0%	0.009
	No	33	1.14 (1.12–1.17)	508.5	93.5%	<0.001	0.002
Excluding IFG from non-cases	Yes	13	1.18 (1.13–1.23)	189.6	93.7%	<0.001
	No	27	1.15 (1.12–1.19)	406.5	93.6%	<0.001	0.42

BMI, body mass index; CI, confidence interval; DM, diabetes mellitus; IFG, impaired fasting glucose; IGT, impaired glucose tolerance; OGTT, oral glucose tolerance test; OR, odds ratio; SNPs, single nucleotide polymorphisms.