Table 2.

Meta-analysis of apolipoprotein E gene polymorphism and MCI risk

Genetic models	Variables	Number of studies	Test of association			Test of heterogeneity
			OR	95% CI	P-value	I2 (%)	Model
ε2/ε2 vs ε3/ε3	Overall	18	0.91	0.50–1.65	0.758	0	F
	Chinese	14	1.04	0.55–1.99	0.902	0	F
ε2/ε4 vs ε3/ε3	Overall	18	2.57	1.77–3.73	<0.001	0	F
	Chinese	14	2.59	1.74–3.86	<0.001	0	F
ε2/ε3 vs ε3/ε3	Overall	18	0.8	0.66–0.97	0.026	0	F
	Chinese	14	0.79	0.64–0.98	0.03	0	F
ε3/ε4 vs ε3/ε3	Overall	18	2.31	1.99–2.69	<0.001	0	F
	Chinese	14	2.34	1.97–2.79	<0.001	5.8	F
ε4/ε4 vs ε3/ε3	Overall	18	4.45	3.06–6.48	<0.001	39.6	F
	Chinese	14	5.45	3.41–8.70	<0.001	0	F
ε4 allele vs ε3 allele	Overall	18	2.38	2.11–2.68	<0.001	42.8	F
	Chinese	14	2.52	2.19–2.90	<0.001	0	F
ε2 allele vs ε3 allele	Overall	18	0.9	0.77–1.05	0.179	32.2	F
	Chinese	14	0.92	0.78–1.09	0.346	30.2	F

Note: P-value corresponding to the Z-test for the summary effect estimate (P<0.05 considered statistically significant).

Abbreviations: F, fixed effects model; OR, odds ratio; CI, confidence interval; I², heterogeneity index; MCI, mild cognitive impairment.