Table 3.
Modified Risk of Bias in Nonrandomized Studies of Interventions table for all studies included in the review
| Study | Confounding | Selection | Classification of exposure | Missing data | Measurement of outcomes | Selective outcome reporting | Overall bias |
| Heitkemper et al. (31) | Serious | Low | Low | Low | Moderate | Moderate | Serious |
| Orr et al. (32) | Serious | Low | Low | Low | Moderate | Moderate | Serious |
| Elsenbruch et al. (33) | Low | Low | Low | Low | Moderate | Serious | Serious |
| Heitkemper et al. (34) | Serious | Low | Low | Low | Moderate | Moderate | Serious |
| Thompson et al. (35) | Serious | Low | Low | Low | Moderate | Serious | Serious |
| Robert et al. (36) | Serious | Low | Low | Low | Moderate | Serious | Serious |
| Waring et al. (37) | Serious | Low | Low | Low | Moderate | Serious | Serious |
| Cain et al. (38) | Serious | Low | Low | Low | Moderate | Critical | Critical |
| Mazur et al. (39) | Critical | Low | Low | Low | Moderate | Moderate | Critical |
| Jarrett et al. (40) | Serious | Low | Low | Moderate | Moderate | Moderate | Serious |
| Pellisier et al. (41) | Serious | Critical | Low | Moderate | Moderate | Serious | Critical |
| Heitkemper et al. (42) | Serious | Low | Low | Low | Moderate | Serious | Serious |
| Mazur et al. (43) | Serious | Low | Low | Low | Moderate | Moderate | Serious |
| Pellisier et al. (44) | Serious | Low | Low | Low | Moderate | Serious | Serious |
| Jarrett et al. (45) | Serious | Low | Critical | Low | Moderate | Serious | Critical |
| Davydov et al. (46) | Serious | Low | Low | Moderate | Moderate | Moderate | Serious |
| Walker et al. (47) | Serious | Low | Low | Low | Low | Moderate | Serious |
| Fournier et al. (48) | Serious | Low | Low | Low | Moderate | Low | Serious |
| Polster et al. (49) | Critical | Low | Low | Low | Low | Moderate | Critical |
| Mouzas et al. (50) | Serious | Low | Low | Low | Moderate | Serious | Critical |
| Furlan et al. (51) | Critical | Low | Low | Low | Moderate | Moderate | Critical |
| Maule et al. (52) | Critical | Low | Low | Low | Moderate | Serious | Critical |
| Coruzzi et al. (53) | Low | Low | Low | Low | Moderate | Moderate | Moderate |
| Ganguli et al. (54) | Serious | Low | Low | Low | Moderate | Serious | Serious |
| Sharma et al. (55) | Serious | Low | Low | Low | Moderate | Moderate | Serious |
| Engel et al. (56) | Low | Low | Low | Low | Moderate | Moderate | Moderate |
| Jelenova et al. (57) | Serious | Low | Low | Serious | Moderate | Low | Serious |
| Gunterberg et al. (58) | Serious | Low | Low | Serious | Moderate | Moderate | Serious |
Pellissier et al. 2010 and 2014 included as study authors compared HRV across all 3 subgroups.
CD, Crohn's disease; HF, high frequency; HRV, heart rate variability; LF, low frequency; MF, moderate frequency; UC, ulcerative colitis; VLF, very low frequency.