Table 2.

Meta-regression analysis of continuous variables.

Sub-group	N	K	Beta	P	Sig.	τ 2	I 2
Age	14	37	−0.0062	0.84	No	0	0
Intervention dose	13	35	0.0167	0.79	No	0.01	3
Daily dose	7	19	0.0002	0.93	No	0.01	6
Dose ratio	7	19	0.009	0.89	No	0.01	5

N, number of studies; K, number of effect sizes; Beta, regression coefficients for between-subgroup comparisons; P, significance value; τ2, measure of variation around average; I2, measure of proportion of observed variance (%).