Global epidemiology of Duchenne muscular dystrophy: an updated systematic review and meta-analysis

Table 2 Results of meta-regression analysis Duchenne Muscular Dystrophy (DMD) prevalence and birth prevalence

Outcome	Subgroup	Study-level covariate(s) included into the meta-regression		Heterogeneity assessment
Outcome	Subgroup	Covariate(s) selected	p-value*	Cochran’s Q (df)	p-value (Q test)	I² (%)	Between-study variance^e	R² (%)^f
DMD prevalence	Males only (15 studies)	None (random-effects MA)	–	856.4531 (df = 14)	< 0.0001	98.46%	0.4741	–
		Continent^a	0.2027	450.7452 (df = 12)	< 0.0001	97.90%	0.3857	18.65%
		Study year (begin) + Study duration	0.4195	632.8951 (df = 12)	< 0.0001	97.89%	0.4227	10.84%
		Study design^c	0.6429	572.9228 (df = 12)	< 0.0001	98.40%	0.4452	6.10%
DMD birth prevalence	All (27 studies)	None (random-effects MA)	–	82.0309 (df = 26)	< 0.0001	89.79%	0.1646	–
		Continent^b	0.9308	74.7046 (df = 23)	< 0.0001	88.90%	0.1619	1.64%
		Study year (begin) + Study duration	0.0012	60.8329 (df = 23)	< 0.0001	83.13%	0.0905	45.02%
		Study design^d	0.3189	78.8714 (df = 24)	< 0.0001	87.51%	0.1483	9.90%

MA Meta-analysis, I² Measure of inconsistency, df Degrees of freedom referred to the Cochran’s Q test
*P-values from omnibus Wald-type test of parameters (i.e. study-level covariates included into the model)
^aContinents were regrouped as follows: America North (US and Canada) (4 studies), Europe North/Centre/East (8 studies), Others (Asia East and Africa South) (3 studies)
^bContinents were regrouped as follows: America North (US and Canada) (4 studies), Asia East and Australia/New-Zealand (4 studies), Europe Centre/East/South (13 studies), Europe North (6 studies)
^cStudy designs were regrouped as follows: Observational cohort (3 studies), Retrospective cohort/chart-review/cross-sectional (9 studies), epidemiological survey (3 studies)
^dStudy designs were regrouped as follows: Cross-sectional (10 studies), Prospective cohort and survey (8 studies), Retrospective cohort/chart-review (9 studies)
^eTotal and residual between-study variance: the overall heterogeneity corresponds to the total between-study variance estimated from random-effects MA whereas the residual heterogeneity corresponds to between study-variance explained by the study-level covariates included into meta-regression model
^fR² is the proportion of the overall heterogeneity (i.e. the total between-study variance) which is “explained” (i.e. reduced) by the effect of the included study-level covariate

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