Study characteristics by registration status
| Registered, n (%) | Not registered, n (%) | Total | P value | |
| 140 (69.0) | 63 (31.0) | 203 | ||
| Industry funding | ||||
| Yes | 132 (80.0) | 33 (20.0) | 165 | <0.001 |
| No | 8 (72.7) | 3 (27.2) | 11 | |
| Not reported | 0 | 27 (100.0) | 27 | |
| Country | ||||
| Multinational | 82 (90.1) | 9 (9.9) | 91 | <0.001 |
| Europe | 26 (50.0) | 26 (50.0) | 78 | |
| North America | 18 (64.2) | 10 (35.7) | 28 | |
| Asia | 6 (23.1) | 20 (76.8) | 26 | |
| South America | 2 (66.7) | 1 (33.3) | 3 | |
| Australia (Oceania) | 0 | 1 (100.0) | 1 | |
| Africa | 1 (100.0) | 0 | 1 | |
| Not reported | 1 (100.0) | 0 | 1 | |
| Clinical condition | ||||
| Alzheimer’s disease | 40 (59.7) | 27 (40.3) | 67 | 0.045 |
| COPD | 100 (73.5) | 36 (26.5) | 136 | |
| Journal impact factor | ||||
| 0–1.999 | 4 (23.5) | 13 (76.5) | 17 | <0.001 |
| 2.000–4.999 | 86 (69.9) | 37 (30.1) | 123 | |
| 5.000–9.999 | 17 (60.7) | 11 (39.3) | 28 | |
| 10.000–14.999 | 14 (87.5) | 2 (12.5) | 16 | |
| ≥15.000 | 19 (100.0) | 0 | 19 | |
| Registration stated in publication | ||||
| Yes | 109 (100.0) | 0 | 109 | <0.001 |
| No | 31 (33.0) | 63 (67.0) | 94 | |
| Sample size | ||||
| 0–49 | 19 (46.3) | 22 (53.7) | 41 | <0.001 |
| 50–99 | 6 (31.6) | 13 (68.4) | 19 | |
| 100–199 | 17 (65.4) | 9 (34.6) | 26 | |
| 200–499 | 41 (75.9) | 13 (24.1) | 54 | |
| 500–999 | 27 (81.8) | 6 (18.2) | 33 | |
| ≥1000 | 30 (100.0) | 0 | 30 |
COPD, chronic obstructive pulmonary disease.