Table 2. Study designs of 838 articles published in 1990, 2000, and 2010.
| Total | Article Year 1990(n = 223) | Article Year 2000(n = 314) | Article Year 2010(n = 301) | χ 2 | P * | |
|---|---|---|---|---|---|---|
| Clinical Design | ||||||
| Descriptive # | 67(8.0%) | 27(12.2%) | 24(7.6%) | 16(5.3%) | 8.118 | 0.017 |
| Case-control | 43(5.1%) | 25(11.2%) | 16(5.1%) | 2(0.7%) | 29.269 | <0.001 |
| Cohort | 49(5.8%) | 5(2.2%) | 14(4.5%) | 30(10.0%) | 15.643 | <0.001 |
| RCT | 679(81.1%) | 166(74.4%) | 260(82.8%) | 253(84.0%) | 8.732 | 0.013 |
| Control Design | ||||||
| Parallel | 687(82.0%) | 170(76.2%) | 261(83.1%) | 256(85.0%) | 7.183 | 0.028 |
| Crossover | 35(4.2%) | 17(7.6%) | 13(4.1%) | 5(1.7%) | 11.379 | 0.003 |
| Factorial | 28(3.3%) | 7(3.2%) | 7(2.2%) | 14(4.7%) | 2.830 | 0.243 |
| Sequential | 10(1.2%) | 4(1.8%) | 3(1.0%) | 3(1.0%) | 0.931 | 0.628 |
| Other | 78(9.3%) | 25(11.2%) | 30(9.6%) | 23(7.6%) | 1.970 | 0.374 |
| Comparison Design | ||||||
| Difference | 463(55.3%) | 167(74.9%) | 154(49.0%) | 142(47.2%) | 47.610 | <0.001 |
| Superiority | 210(25.1%) | 33(14.8%) | 85(27.1%) | 92(30.6%) | 18.037 | <0.001 |
| Non-inferiority | 138(16.5%) | 18(8.1%) | 65(20.7%) | 55(18.3%) | 16.230 | <0.001 |
| Equality | 27(3.2%) | 5(2.2%) | 10(3.2%) | 12(4.0%) | 1.253 | 0.535 |
| Primary endpoint | ||||||
| 675(80.6%) | 129(57.8%) | 264(84.1%) | 282(93.7%) | 109.009 | <0.001 |
# Descriptive: cross-sectional study, sampling survey and prevalence study;
*Chi-square test for differences among years.