Table 2.
Study population, random-effects meta-analyses raw (A) and heterogeneity analyses (B).
| (A) Raw Analyses | PD Patients | Controls | SMD | ci.lb | ci.ub | p value | I2 (%) | Tau2 | k |
| HF (ms2) | 145.2 ± 41.1 | 219.4 ± 48.8 | −1.38 | −2.17 | −0.58 | 0.002 | 91 | 3.27 | 23 |
| HF (nu) | 34.7 ± 1.8 | 33.2 ± 1.9 | 0.08 | −0.93 | 1.09 | 0.867 | 96 | 3.99 | 18 |
| RMSSD (ms) | 23.4 ± 1.9 | 28.9 ± 1.8 | −0.58 | −1.18 | 0.02 | 0.059 | 92 | 1.35 | 18 |
| pNN50 (%) | 4.7 ± 1.1 | 6.8 ± 1.3 | −0.46 | −1.54 | 0.63 | 0.378 | 96 | 3.39 | 14 |
| (B) Heterogeneity Analyses | PD Patients | Controls | SMD | ci.lb | ci.ub | p value | I2 (%) | Tau2 | k |
| HF (ms2) | 107.7 ± 11.0 | 183.0 ± 22.0 | −0.79 | −1.13 | −0.45 | <0.001 | 67 | 0.28 | 14 |
| HF (nu) | 34.5 ± 3.3 | 33.8 ± 3.2 | 0.04 | −0.29 | 0.36 | 0.810 | 53 | 0.12 | 9 |
| RMSSD (ms) | 21.7 ± 1.2 | 24.7 ± 1.1 | −0.65 | −0.97 | −0.32 | 0.001 | 66 | 0.18 | 12 |
| pNN50 (%) | 3.5 ± 0.5 | 5.5 ± 0.8 | −0.59 | −1.06 | −0.12 | 0.020 | 64 | 0.28 | 9 |
Values are given as mean or as mean ± SD, unless otherwise indicated: (A) raw analyses; (B) heterogeneity analyses; ci.lb: confidence interval lower bound; ci.ub: confidence interval upper bound; HF: high frequency components of the power spectral density; HRV: heart rate variability; k: number of considered studies; nu: normalized units; PD: Parkinson’s disease; pNN50: number of normal-to-normal intervals differing by more than 50 ms divided by the total number of normal-to-normal intervals; RMSSD: Root mean square of successive normal-to-normal interval differences; SMD: standardized mean differences.