Table 5.

A categorization of the articles based on the US Task Force evidence classification, modified by Tutak M et al. [35]

US Task Force Level of evidence	Study design	No (%) of published articles	Bibliography numbers
Age group I. Mother/baby approach/pre-school children at baseline (≤5-yr- olds) (n = 19)
I:	Randomized controlled trials	8 (42%)	[36–39, 57, 77, 78, 82]
II-1:	Controlled trials without randomization	3 (16%)	[58, 65, 68]
II-2:	Cohort or case-controlled studies	7 (37%)	[63, 66, 69–71, 79, 80]
II-3:	Case series	1 (5%)	[52]
III	Case reports, Opinions of authorities	0
Age group II. Schoolchildren and adolescents (n = 18)
I:	Randomized controlled trials	6 (33%)	[40–44, 81]
II-1:	Controlled trials without randomization	2 (11%)	[62, 76]
II-2:	Cohort or case-controlled studies	8 (45%)	[56, 59–61, 64, 67, 72, 73]
II-3	Case series	2 (11%)	[74, 75]
III	Case reports, opinions of authorities	0