Table 1.
Characteristics of included studies with meta-regression analysis
| Characteristics | Total (N = 81) | Year 2002 (N = 29) | Year 2012 (N = 52) |
|---|---|---|---|
| Journal characteristics | |||
| Journal Impact Factor, median (IQR) | 4.2 (2.3–6.1) | 4.4 (2.9–5.6) | 3.9 (2.0–6.6) |
| General medical journal | 15 (19%) | 5 (17%) | 10 (19%) |
| Core clinical journals | 19 (23%) | 9 (31%) | 10 (19%) |
| Author characteristics | |||
| Affiliated with industry | 5 (6%) | 3 (10%) | 2 (4%) |
| Affiliated with biostatistics or epidemiology department | 35 (43%) | 16 (55%) | 19 (37%) |
| Ten or more of studies | 73 (90%) | 26 (90%) | 47 (90%) |
| Drug intervention | 38 (47%) | 15 (52%) | 23 (44%) |
| Type of outcome in meta-regression analysis | |||
| Binary | 39 (48%) | 13 (45%) | 26 (50%) |
| Continuous | 48 (59%) | 18 (62%) | 30 (58%) |
| Clinical field | |||
| Psychiatry & Psychology | 13 (16%) | 5 (17%) | 8 (15%) |
| Cardiology | 10 (12%) | 3 (10%) | 7 (13%) |
| Oncology | 8 (10%) | 1 (3%) | 7 (13%) |
| Infectious disease | 7 (9%) | 2 (7%) | 5 (10%) |
| Endocrinology & Metabolism | 7 (9%) | 3 (10%) | 4 (8%) |
| Surgery | 6 (7%) | 0 (0%) | 6 (12%) |
| General internal medicine | 5 (6%) | 3 (10%) | 2 (4%) |
| Paediatrics | 4 (5%) | 2 (7%) | 2 (4%) |
| Nutrition & dietetics | 4 (5%) | 0 (0%) | 4 (8%) |
| Rheumatology | 4 (5%) | 3 (10%) | 1 (2%) |
| Miscellaneous | 13 (16%) | 7 (24%) | 6 (12%) |
There were no important differences in baseline characteristics between the two assessed years