Table 2. Baseline characteristics of participants.
| Study | Participants | Gender (male/female) | Age of test/control (years), (range or mean ± SD) | Test group (n) | Control group (n) |
|---|---|---|---|---|---|
| Godoy 2012, (14) | Patients and matching controls | 1,507/1,580 | 38.48±22.79/39.13±22.68 | 813 | 2,274 |
| Lau 2004, (15) | Patients and matching controls | 475/515 | ≥16 | 330 | 660 |
| Merk 2014, (37) | All | 1,053/1,811 | 56.40/46.30 | 2,513 | 351 |
| Huang 2007, (20) | AIDS patients | 111/37 | 43.70±11.00/41.90±11.00 | 75 | 73 |
| Mangklakeree 2014, (27) | Elementary school student | 216/238 | – | 175 | 279 |
| Torner 2015, (26) | Patients and matching controls | 269/209 | 5.40±4.50/5.30±4.60 | 239 | 239 |
| Thumma 2009, (38) | Freshman students | 215/243 | 18.50 | 143 | 319 |
| Chen 2011, (25) | All | – | – | 35 | 97 |
SD, standard deviation; AIDS, acquired immune deficiency syndrome; –, unavailable.