Table 1.
Characteristics of included surgical randomized trials
| 1999 (n = 300) | 2009 (n = 450) | RR*†^ | P† | 2019 (n = 438) | RR* | P~ | |
|---|---|---|---|---|---|---|---|
| Region | |||||||
| Africa/South America | 6 (2.0) | 31 (6.8) | 3.44 (1.45, 8.16) | 0.002 | 30 (6.8) | 0.99 (0.61, 1.61) | 1.000 |
| Asia/Oceania | 61 (20.3) | 159 (35.3) | 1.74 (1.34, 2.25) | <0.001 | 199 (45.4) | 1.29 (1.09, 1.51) | 0.002 |
| Europe | 161 (53.6) | 204 (45.3) | 0.84 (0.73, 0.98) | 0.031 | 154 (34.2) | 0.78 (0.66, 0.91) | 0.002 |
| North America | 72 (24.0) | 56 (12.4) | 0.52 (0.38, 0.71) | <0.001 | 55 (12.6) | 1.01 (0.71, 1.43) | 1.000 |
| Countries | |||||||
| Single country (versus multinational) | 273 (91.0) | 408 (90.6) | 1.04 (0.65, 1.64) | 0.898 | 380 (86.8) | 0.96 (0.91, 1.00) | 0.071 |
| Centres | |||||||
| Single centre (versus multicentre) | 173 (57.7) | 270 (60.0) | 1.04 (0.92, 1.18) | 0.545 | 279 (63.7) | 1.06 (0.96, 1.18) | 0.269 |
| Specialty | |||||||
| Gastrointestinal surgery | 156 (52.0) | 203 (45.1) | 0.87 (0.75, 1.01) | 0.086 | 222 (50.7) | 1.12 (0.98, 1.29) | 0.107 |
| Trauma | 19 (6.3) | 19 (4.2) | 0.67 (0.36, 1.24) | 0.234 | 16 (3.6) | 0.87 (0.45, 1.66) | 0.732 |
| Vascular surgery | 46 (15.3) | 62 (13.8) | 0.90 (0.63, 1.28) | 0.596 | 34 (7.7) | 0.56 (0.38, 0.84) | 0.004 |
| Other‡ | 79 (26.3) | 166 (36.9) | 1.40 (1.12, 1.75) | 0.003 | 166 (37.9) | 1.03 (0.87, 1.22) | 0.782 |
| Malignancy | |||||||
| Benign disease§ | 196 (65.3) | 287 (63.8) | 0.98 (0.88, 1.09) | .697 | 223 (50.9) | 0.80 (0.71, 0.90) | <0.001 |
| Malignant disease§ | 80 (26.7) | 102 (22.7) | 0.85 (0.66, 1.10) | .224 | 160 (36.5) | 1.61 (1.31, 1.99) | <0.001 |
| Both | 6 (2.0) | 18 (4.1) | 2,00 (0,80, 4,98) | 0.143 | 48 (11.0) | 2.74 (1.62, 4.63) | <0.001 |
| Unclear | 18 (6.0) | 43 (9.6) | 1.59 (0.94, 2.71) | 0.101 | 7 (1.6) | 0.17 (0.08, 0.37) | <0.001 |
| Type of intervention studied | |||||||
| Surgical procedure | 112 (37.3) | 212 (47.1) | 1.26 (1.06, 1.51) | 0.009 | 243 (55.5) | 1.18 (1.04, 1.34) | 0.013 |
| Medication | 133 (44.3) | 144 (32.0) | 0.72 (0.60, 0.87) | 0.001 | 66 (15.1) | 0.47 (0.36, 0.61) | <0.001 |
| Other | 55 (18.3) | 94 (20.9) | 1.14 (0.85, 1.54) | .402 | 129 (29.5) | 1.41 (1.12, 1.78) | 0.003 |
| Type of reference intervention¶ | |||||||
| Similar surgery | 71 (63.3) | 138 (65.1) | – | 0.752 | 173 (71.2) | – | 0.005 |
| Different surgery | 31 (27.7) | 50 (23.5) | 62 (25.5) | ||||
| Non-surgical invasive | 2 (1.8) | 7 (3.3) | 3 (1.2) | ||||
| Non-surgical non-invasive | 8 (7.1) | 17 (8.0) | 5 (2.1) | ||||
| Specialty of journal | |||||||
| Surgical journals | 177 (59.0) | 240 (53.3) | 0.90 (0.80, 1.03) | .134 | 214 (48.9) | 0.92 (0.81, 1.04) | 0.202 |
| Impact factor# | 274 (91.3) | 375 (83.3) | 426 (97) | ||||
| Median (i.q.r.) | 2.24 (1.13– 3.00) | 2.57 (1.86– 3.72) | – | <0.001 | 2.80 (1.68– 4.51) | – | 0.048 |
| Journal rank# | |||||||
| Top 10 surgery | 29 (9.7) | 56 (12.4) | 1.41 (0.92, 2.14) | 0.126 | 53 (12.1) | 0.81 (0.57, 1.15) | 0.919 |
| Top 10 general | 14 (4.7) | 8 (1.7) | 0.42 (0.18, 0.98) | 0.048 | 10 (2.3) | 1.07 (0.43, 2.69) | 0.640 |
| Trial design | |||||||
| Parallel (versus crossover) | 300 (100) | 435 (96.7) | 1.01 (0.98, 1.04) | 0.503 | 431 (98.4) | 1.02 (1.00, 1.04) | 0.477 |
| Sample size, median (i.q.r.) | 70 (40–151) | 78 (47–141) | – | 0.233 | 10 050 (64– 190) | – | <0.001 |
| Funding | |||||||
| Industry funded | 68 (22.7) | 83 (18.4) | 0.81 (0.61, 1.08) | 0.164 | 50 (11.4) | 0.62 (0.45, 0.86) | 0.003 |
| Non-industry funded | 61 (20.3) | 177 (39.3) | 1.93 (1.50, 2.49) | <0.001 | 236 (53.9) | 1.37 (1.19, 1.58) | <0.001 |
| Not reported | 171 (57.0) | 190 (42.2) | 0.74 (0.64, 0.86) | <0.001 | 152 (34.7) | 0.82 (0.70, 0.97) | 0.021 |
| Funding reported+ | |||||||
| Industry funded | 68 (52.7) | 83 (31.9) | 0.61 (0.48, 0.77) | <0.001 | 50 (17.5) | 0.55 (0.40, 0.75) | <0.001 |
| Non-industry funded | 61 (47.2) | 177 (68.0) | 1.44 (1.18, 1.76) | <0.001 | 236 (82.5) | 1.21 (1.10, 1.34) | <0.001 |
Values are n (%) unless indicated otherwise; *values in parentheses are 95% confidence intervals. †This comparison was performed in the authors’ previous study8. +Analysis excluding the less informative ‘not reported’ group was added to aid interpretation of results. The relationship observed over time regarding industry funding persisted and relative differences were more pronounced. ‡Includes breast, abdominal wall, thoracic, and endocrine surgery. §Analysis excluding the less informative ‘unclear’ group showed similar results regarding the trend for benign and malignant disease over time. ¶For trials studying surgical interventions only. #On the basis of impact factors of the Institute for Scientific Information for the respective year (1999, 2009, 2019). Journals without an impact factor are not included. ^Comparing 1999 and 2009 using Fisher’s exact, χ2, and Mann–Whitney U tests. ~Comparing 2009 and 2019 using Fisher’s exact, χ2, and Mann–Whitney U tests. RR, relative rate.