Overall study characteristics
| Characteristics | Frequency |
| Average number of patients | 90.8 |
| Average patient age | 58.5 |
| Male patients, % | 74.7 |
| Average number of study groups | 2 |
| Level of evidence | |
| I | 12 |
| II | 0 |
| III | 0 |
| IV | 0 |
| Study design | |
| Randomized control trial | 12 |
| Years published | |
| 2010–present | 5 |
| 2000–2009 | 6 |
| 1990–1999 | 1 |