Table 1.
Study characteristics.
| Study characteristics | Number (%) of references (n = 70) |
|---|---|
| Country of publication | |
| Germany | 41 (58.6%) |
| United States of America | 14 (20.0%) |
| Other European countries | 13 (18.6%) |
| Canada | 1 (1.4%) |
| Israel | 1 (1.4%) |
| Year of publication | |
| 1991–2000 a | 9 (12.9%) |
| 2001–2010 | 26 (37.1%) |
| 2011–2021 | 35 (50%) |
| Publication design | |
| Randomized control trial | 1 (1.4%) |
| Cross-sectional study | 59 (84.3%) |
| Longitudinal study | 7 (10.0%) |
| Retrospective study | 2 (2.9%) |
| Case-control study | 1 (1.4%) |
a
First paper was published in 1993.