Table 1.
General characteristics of included studies (n = 28)
| Characteristic | Categories | No. (%) |
|---|---|---|
| Country or region | China | 6 (21) |
| Korea | 5 (18) | |
| Japan | 13 (46) | |
| Poland | 1 (4) | |
| Taiwan | 3 (11) | |
| Research design | RCT | 17 (61) |
| NRCT | 11 (39) | |
| Participant | Healthy people | 17 (61) |
| People with health problems | 11 (39) | |
| Average age (years) | 18 ≤ | 1 (3.5) |
| > 18 ≤ 30 | 12 (43) | |
| > 30 ≤ 45 | 1 (3.5) | |
| > 45 | 12 (43) | |
| Age unknown | 2 (7) | |
| Sample size | ≤ 20 | 8 (29) |
| > 20 ≤ 50 | 7 (25) | |
| > 50 | 13 (46) | |
| Time | 3 days ≤ | 20 (71) |
| > 3 days | 8 (29) | |
| Ethical consideration | Yes | 25 (89) |
| No | 3 (11) | |
| Interdisciplinary research | Yes | 3 (11) |
| No | 25 (89) |