Table 2.
Characteristics of the 20 included studies in the systematic review and meta-analysis
| Study | Newcastle–Ottawa Scale | Country | Sex | Sample size | Age, years (mean ± SD or range) |
Participants | Genotyping |
|---|---|---|---|---|---|---|---|
| Cieszczyk et al. 2011 [30] | 8 | Poland | Men | Elite athletes (N = 44) | 23–61 | Elite rowers, non-elite rowers and controls (students from the University of Szczecin) | PCR–RFLP |
| Non-elite athletes (N = 83) | 18–41 | ||||||
| Controls (N = 251) | 19–23 | ||||||
| Cieszczyk et al. 2012 [29] | 8 | Poland | Men | Elite athletes (N = 158) | 19–34 | Power-oriented athletes, sub-elite and controls (students from the University of Szczecin) | PCR–RFLP |
| Sub-elite athletes (N = 134) | 19–23 | ||||||
| Controls (N = 160) | |||||||
| Dionísio et al. 2017 [46] | 6 | Brazil | Men | Athletes (N = 220) | 14–20 | Professional minor league of the soccer team | qPCR |
| Djarova et al. 2013 [43] | 7 | Bulgaria | Men | Athletes (N = 5) | 50 ± 14.6 | Elite high-altitude mountaineers and controls (students) | PCR–RFLP |
| Controls (N = 72) | 21.5 ± 1.8 | ||||||
| Fedotovskaya et al. 2013 [12] | 8 | Russia | Men and women | Athletes (N = 305) | High-speed and strength sports and controls (high school students) | PCR–RFLP | |
| Men: 252 | 21.2 ± 4.3 | ||||||
| Women: 53 | 25.7 ± 3.1 | ||||||
| Controls (N = 499) | |||||||
| Men: 139 | 19.6 ± 2.1 | ||||||
| Women: 360 | 18.0 ± 3.3 | ||||||
| Ginevičienė et al. 2014 [11] | 8 | Lithuania | Men and women | Athletes (N = 204) | 22.0 ± 6.3 | Endurance and power-oriented athletes and controls (healthy unrelated individuals) | PCR–RFLP |
| Men: 160 | |||||||
| Women: 44 | |||||||
| Controls (N = 260) | 36.2 ± 7.2 | ||||||
| Grealy et al. 2015 [13] | 6 | Australia | Men | Athletes (N = 196) |
25 ± 5.4 21.1 ± 2 |
Elite endurance triathletes | PCR–RFLP |
| Gronek et al. 2018 [31] | 6 | Poland | Men | Athletes (N = 180) | 18–65 | Experienced half marathon runners | PCR–RFLP |
| Horozoglu et al. 2021 [47] | 6 | Turkey | Men | Athletes (N = 33) | 18–25 | Super amateur league football players | qPCR |
| Maestro et al. 2022 [48] | 6 | Spain | Men | Athletes (N = 122) | Data not shown | Professional soccer players | PCR–RFLP |
| Meckel et al. 2012 [42] | 8 | Israel | Men and women |
Athletes (N = 155) Men: 119 Women: 36 Controls (N = 142) Men: 100 Women: 42 |
35.9 ± 12.2 | Endurance and sprint athletes and non-athletic healthy individuals | PCR–RFLP |
| Muniesa et al. 2010 [49] | 8 | Spain | Men |
Athletes (N = 141) Rowers: 39 Olympic-class runners: 52 Professional road cyclists: 50 Controls (N = 132) |
Data not shown | Runners, cyclists, rowers and healthy, non-athletic individuals | PCR–RFLP |
| Petr et al. 2022 [50] | 8 | Czech Republic | Men | Athletes (N = 99) | 25.4 ± 4.51 | Elite soccer players and controls (healthy subjects) | PCR–RFLP |
| Controls (N = 107) | 18–65 | ||||||
| Pranckeviciene et al. 2021 [51] | 8 | Lithuania | Men and women |
Athletes (N = 180) Men: 130 Women: 50 Controls (N = 255) |
26.4 ± 6.7 | Elite athletes | PCR–RFLP |
| Ruiz et al. 2009 [15] | 8 | Spain | Men |
Athletes (N = 46) Endurance runners: 14 Professional road cyclists: 32 Controls (N = 123) |
Data not shown | Endurance runners, professional road cyclists and controls (healthy male non-athletic individuals) | PCR–RFLP |
| Santiago et al. 2010 [44] | 8 | Spain | Men |
Athletes (N = 53) World-class rowers: 39 National-class rowers:15 Controls (N = 123) |
Data not shown | World-class rowers, national-class rowers and controls (healthy male non-athletic individuals) | PCR–RFLP |
| Tsianos et al. 2009 [52] | 6 | Greece | Men and women |
Athletes (N = 438) Men: 417 Women:21 |
38.4 ± 8.3 | Olympus marathon runners | PCR–RFLP |
| Varillas Delgado et al. 2020 [41] | 8 | Spain | Men | Athletes (N = 123) | Professional road cyclists, elite endurance runners and controls (non-athlete participants) | PCR–RFLP | |
| Professional road cyclists: 75 |
25.8 ± 4.2 (18–42) |
||||||
| Elite endurance runners: 48 |
27.9 ± 5.1 (19–42) |
||||||
| Controls (N = 122) | |||||||
| Varillas Delgado et al. 2022 [53] | 8 | Spain | Men |
Endurance athletes (N = 160) Professional football players (N = 132) Non-athletes (N = 160) |
Data not shown | Professional cyclists, elite long-distance runners, professional football players and non-athlete individuals (non-smokers, and not suffering from chronic or acute diseases, or obesity) | PCR–RFLP |
| Varillas Delgado et al. 2022 [54] | 6 | Spain | Men and women |
Athletes (N = 100) Men: 50 Women: 50 |
Data not shown | Elite endurance athletes | PCR–RFLP |
PCR–RFLP polymerase chain reaction-restriction fragment length polymorphism, qPCR quantitative polymerase chain reaction