Table 4. Heterogeneity analysis for hospital-based and population-based studies.

	Heterogeneity statistics	Degree of freedom	P	I-squared**	Tau-squared	z test	p value
Hospital based	617.12	16	0.000	97.4%	0.0002	8.57	0.000
Population based	39.16	4	0.000	89.8%	0.0000	3.51	0.000
Overall	684.91	21	0.000	96.9%	0.0001	7.92	0.000

**I-squared: the variation in Effect Size attributable to heterogeneity.

Note: Between-group heterogeneity was not calculated. Significance test(s) of ES  = 0.