Table 3. Meta-regression analysis on 15 selected studies (Table 1).

Sources of heterogeneity	Coefficient	95%CI		P
		Lower	Upper
Publication year	1.2831	−0.3213	2.8875	0.1170
Ethnicity	1.2830	−2.5690	5.1351	0.5139
Method	−1.9797	−5.9054	1.9461	0.3230
Source of controls	0.3772	−1.3829	2.1373	0.6745
Case sample size	−0.7374	−2.1433	0.7964	0.3460