*4.1. Meta-Analysis*

### 4.1.1. Study Inclusion and Data Characteristics

Our PubMed search yielded a total of 777 studies. Four duplicates were removed, leaving 773 studies for title and abstract screening. Here, 538 studies did not fulfil the inclusion criteria. The remainder of 235 full-text studies were assessed for eligibility. Four additional studies were identified through cross-reference screening and added to the eighty-three studies selected for data extraction, involving 1652 patients (Figure 1, Supplementary Table S1). Data exhibited a nonparametric distribution.

### 4.1.2. DBS parameters and Tremor Outcomes

The correlation coefficients of the stimulation parameters with time were r(1159) = −0.17, r2 = 0.02 (2.89%), *p* < 0.001 for voltage, r(1312) = −0.17, r2 = 0.02 (2.89%) *p* < 0.001 for pulse width and r(1258) = 0.08, r2 = 0.006 (0.6%) *p* < 0.05 for frequency. Overall, the average tremor suppression achieved by DBS was 62.98% ± 16%, r(1466) = 0.16, r2 = 0.02 (2.56%), *p* < 0.001 (Supplementary Figure S1).

### 4.1.3. Correlation of Stimulation Parameters and Tremor Suppression

Follow-up times were split into quartiles, which yielded four groups of tremor outcomes corresponding to reports ranging from 3 to 6 months, 7 to 12 months, 13 to 30 months and 31 to 150 months, respectively. Although tremor outcomes differed significantly between the four groups (χ2(3) = 186, *p* < 0.001), the means did not exhibit a consistent downward trend (M1 = 57.42, 95% CI: 55.78–59.08; M2 = 70.93, 95% CI: 69.8–72.02; M3 = 62.25, 95% CI: 60.47–64.14; M4 = 55.95, 95% CI: 53.73–58.16). Thus, no correction for the variable follow-up times was applied. Regarding the interdependence of stimulation parameters and tremor, an inverse relationship is observed between voltage r(1159) = −0.09, r2 = 0.008 (.81%), *p* < 0.05, and tremor. Although the same trend is observed for pulse width r(1312) = −0.06, r2 = 0.003 (0.36%), *p* = 0.05, and frequency r(1258) = −0.03, r2 = 0.0009 (0.09%), *p* = 0.28, these are not statistically significant.
