Table 3. Subgroup analysis results.

F: fixed effects model; R: random effects model.

	Studies	Number of patients	R(95%CI)	Heterogeneity test	Effects model	Venice Rating	Overall credibility
Low latitude	5	415	-0.26(-0.35,-0.16)	I2 = 16%, P = 0.31	F	BAA	Moderate evidence
Middle latitude	9	1834	-0.11(-0.15,-0.06)	I2 = 38%, P = 0.10	F	AAA	Strong evidence
Developed countries	8	1723	-0.11(-0.16,-0.06)	I2 = 0%, P = 0.47	R	AAA	Strong evidence
Developing countries	6	526	-0.21(-0.36,-0.06)	I2 = 67%,P = 0.01	R	BCA	Weak evidence