30. Risk of bias by publication year.

All studies included	Low risk of bias		Unclear risk of bias		High risk of bias		Total
Publication year	N	Row %	N	Row %	N	Row %
1971 to 1980	0	0%	1	20%	4	80%	5
1981 to 1990	2	29%	0	0%	5	71%	7
1991 to 2000	3	20%	6	40%	5	40%	15
2001 to 2010	21	39%	23	43%	10	18%	54
2011 to 2019	27	47%	24	42%	6	11%	57
Total	53	36%	54	42%	30	22%	138
Only safety studies	Low risk of bias		Unclear risk of bias		High risk of bias		Total
Publication year	N	Row %	N	Row %	N	Row %
1971 to 1980			1	20%	4	80%	5
1981 to 1990	2	29%			5	71%	7
1991 to 2000	2	20%	4	40%	4	40%	10
2001 to 2010	17	40%	17	41%	8	19%	43
2011 to 2019	17	74%	5	22%	1	4%	22
Total	38	39%	27	37%	22	24%	87