Publication characteristics
| Characteristic | Variables | ||
| N (%) | 95% CI | ||
| Test subjects (n=296) | Animals | 5 (1.69) | — |
| Humans | 189 (63.85) | — | |
| Both | 0 (0) | — | |
| Neither | 102 (34.46) | — | |
| Country of journal publication (n=296) | USA | 130 (43.92) | — |
| UK | 19 (6.42) | — | |
| Australia | 16 (5.41) | — | |
| Netherlands | 15 (5.07) | — | |
| Germany | 15 (5.07) | — | |
| Canada | 12 (4.05) | — | |
| China | 11 (3.72) | — | |
| Italy | 8 (2.7) | — | |
| France | 6 (2.03) | — | |
| Spain | 5 (1.69) | — | |
| Portugal | 5 (1.69) | — | |
| Israel | 5 (1.69) | — | |
| Brazil | 5 (1.69) | — | |
| Unclear | 3 (1.01) | — | |
| Other | 41 (13.85) | — | |
| Country of corresponding author (n=296) | USA | 155 (52.36) | — |
| UK | 86 (29.05) | — | |
| Netherlands | 32 (10.81) | — | |
| Ireland | 8 (2.7) | — | |
| Germany | 5 (1.69) | — | |
| Switzerland | 3 (1.01) | — | |
| France | 3 (1.01) | — | |
| Canada | 1 (0.34) | — | |
| Brazil | 1 (0.34) | — | |
| Australia | 1 (0.34) | — | |
| Unclear | 1 (0.34) | — | |
| Open access (n=296) | Yes found via Open Access Button | 95 (32.1) | 26.8–37.4 |
| Yes found article via other means | 12 (4.1) | 1.8–6.3 | |
| Could not access through paywall | 189 (63.9) | 58.4–69.3 | |
| 5-year impact factor (n=296) | Median | 3.2 | — |
| First quartile | 2.2 | — | |
| Third quartile | 4.2 | — | |
| IQR | 2.2–4.2 | — | |
| Most recent impact factor year (n=296) | 2014 | 0 | — |
| 2015 | 0 | — | |
| 2016 | 0 | — | |
| 2017 | 270 | — | |
| 2018 | 0 | — | |
| Other | 30 | — | |
| Most recent impact factor (n=296) | Median | 3 | — |
| First quartile | 1.9 | — | |
| Third quartile | 4 | — | |
| IQR | 1.9–4.0 | — | |