Table 2.

NOS of the included studies

NOS	Percentages of studies N(n%)*	References of studies
8☆	14 (26%)	[11,14,27,32,38,39,41,43,45,48,50,54,56,63]
7☆	22 (41%)	[15,18,20-23,26,29,35-37,47,49,51,52,55,57-62,64]
6☆	18 (33%)	[12,13,16,17,19,24,25,28,30,31,33,34,40,42,44,46,53]

*N (n%), N = number of studies, n = percentage in the 54 included studies.