Table 2.

Summary of pooled ORs with CI in the meta-analysis

Group	No. of studies	Heterogeneity		Significant		OR (95%CI)	Model
		I2 (%)	Pheterogeneity	Z	P
Overall	5	77.7	0.001	2.56	0.011	0.68 (0.50–0.91)	Random
Study design
Case–control studies	2	80.8	0.023	0.29	0.774	0.89 (0.40–1.99)	Random
Cohort studies	3	83.3	0.002	2.36	0.018	0.61 (0.41–0.92)	Random
Geographic locations
Western	3	65.9	0.053	0.41	0.685	0.89 (0.52–1.54)	Random
Eastern	2	90.6	0.001	2.52	0.012	0.55 (0.35–0.88)	Random
Sample size
< 10,000	2	80.8	0.023	0.29	0.774	0.89 (0.40–1.99)	Random
≥ 10,000	3	83.3	0.002	2.36	0.018	0.61 (0.41–0.92)	Random
Quality
Moderate	1	NA	NA	0.03	0.979	0.99 (0.46–2.12)	NA
High	4	82.0	0.001	2.65	0.008	0.65 (0.47–0.89)	Random

OR: odds ratio; CI: confidence Interval; NA: not applicable