Table 2. Study Characteristics Stratified by Study Design Characteristics.
| Study Characteristic | No. (%) of Studies | χ2 P Value | No. (%) of Studies | χ2 P Value | |||
|---|---|---|---|---|---|---|---|
| All (N = 1783) | Observational (n = 213) | Interventional (n = 1570) | Nonrandomized (n = 519) | Randomized (n = 1257) | |||
| Start year | |||||||
| Before 2011 | 244 (13.7) | 27 (12.7) | 215 (13.7) | .26 | 53 (8.6) | 185 (13) | .26 |
| 2011 | 97 (5.4) | 14 (6.6) | 83 (5.3) | 31 (5.6) | 66 (5.1) | ||
| 2012 | 119 (6.7) | 13 (6.1) | 106 (6.8) | 37 (6.2) | 82 (6.3) | ||
| 2013 | 200 (11.2) | 27 (12.7) | 173 (11) | 53(10) | 147 (12) | ||
| 2014 | 259 (14.5) | 35 (16.4) | 224 (14.3) | 81 (16) | 178 (15) | ||
| 2015 | 334 (18.7) | 41 (19.2) | 293 (16.7) | 100 (20) | 234 (20) | ||
| 2016 | 415 (23.3) | 47 (22) | 368 (23.4) | 132 (28) | 282 (23) | ||
| 2017 | 108 (6.1) | 9 (8.3) | 101 (6.4) | 30 (5.4) | 79 (6.5) | ||
| Not stated | 7 (0.4) | NA | 7 (0.4) | 2 | 4 | ||
| Target agea | |||||||
| Child (<18 y) | 374 (20.1) | 45 (21.1) | 329 (21) | .95 | 117 (22.5) | 253 (20.1) | .25 |
| Adult (18-65 y) | 1680 (94.2) | 204 (95.8) | 1476 (94) | .30 | 487 (93.8) | 1186 (94.3) | .67 |
| Senior (≥66 y) | 1302 (73) | 174 (81.7) | 1128 (71.8) | .002 | 387 (74.5) | 908 (72.2) | .31 |
| Target sex | |||||||
| Men only | 34 (1.9) | 2 (0.9) | 32 (2.0) | .005 | 7 (1.4) | 27 (2.1) | .04 |
| Women only | 139 (9.0) | 10 (4.7) | 129 (8.22) | 33 (6.4) | 106 (8.4) | ||
| Both | 1607 (89) | 199 (93.4) | 1408 (89.7) | 477 (91.9) | 1124 (89.4) | ||
| Not stated | 3 (0.1) | 2 (0.9) | 1 (0.06) | NA | NA | ||
| Clinical area | |||||||
| Autoimmune | 84 (4.7) | 5 (2.3) | 79 (5.0) | <.001 | 20 (3.9) | 64 (5.1) | <.001 |
| Cardiometabolic | 382 (21.4) | 44 (20.7) | 338 (21.5) | 94 (18.1) | 287 (2.9) | ||
| Hematology-oncology | 107 (6) | 10 (4.7) | 97 (6.2) | 38 (7.3) | 69 (5.5) | ||
| Infectious disease | 77 (4.3) | 5 (2.4) | 72 (4.6) | 13 (2.5) | 64 (5.1) | ||
| Mental health | 216 (12.1) | 15 (7.0) | 201 (12.8) | 51 (9.8) | 163 (13) | ||
| Musculoskeletal or pain | 54 (3) | 6 (2.8) | 48 (3.1) | 12 (2.3) | 41 (3.3) | ||
| Neurology | 114 (6.4) | 29 (13.7) | 85 (5.4) | 58 (11.2) | 56 (4.5) | ||
| Obstetrics-gynecology | 63 (3.5) | 10 (4.7) | 53 (3.4) | 20 (3.9) | 43 (3.4) | ||
| Pulmonary | 113 (6.3) | 15 (7.0) | 98 (6.2) | 37 (7.1) | 76 (6.1) | ||
| Renal | 24 (1.4) | 3 (1.4) | 21 (1.3) | 8 (1.5) | 16 (1.3) | ||
| Substance abuse | 112 (6.3) | 9 (4.2) | 103 (6.6) | 21 (4.1) | 91 (7.2) | ||
| Surgery | 32 (1.8) | 7 (3.3) | 25 (1.6) | 14 (2.7) | 17 (1.4) | ||
| Wellness | 183 (10.2) | 4 (2.2) | 179 (11.4) | 35 (6.7) | 146 (11.6) | ||
| Other | 222 (12.4) | 51 (23.9) | 171 (10.9) | 98 (18.9) | 124 (9.9) | ||
| Fundingb | |||||||
| NIH or federal | 369 (20.7) | 31 (14.6) | 338 (21.5) | .02 | 72 (13.9) | 294 (23.4) | <.001 |
| Commercial or industry | 214 (12.0) | 48 (22.5) | 166 (0.6) | <.001 | 88 (17.0) | 125 (9.9) | <.001 |
| Other | 1602 (91) | 184 (86.4) | 1418 (90.3) | .07 | 467 (89.9) | 1131 (70.8) | >.99 |
| Trial size | |||||||
| 0-100 | 829 (46.5) | 102 (47.9) | 727 (46.3) | .002 | 317 (61.1) | 508 (40.4) | <.001 |
| 101-1000 | 812 (45) | 82 (38.5) | 730 (46.5) | 154 (29.7) | 657 (52.3) | ||
| >1000 | 142 (8.0) | 29 (13.7) | 113 (7.2) | 48 (9.3) | 92 (7.3) | ||
Abbreviations: NA, not applicable; NIH, National Institutes of Health.
a
Some studies listed multiple funding sources and target audiences.