*Primary Outcomes*

Baseline demographics between the groups are outlined in Table 1.


#### **Table 1.** Baseline demographics by groups.

BP, blood pressure; CAG, cytosine-adenine-guanine; JOHD, juvenile-onset Huntington's Disease; SD, standard deviation; SES, socioeconomic status.

Participants in the JOHD group had significant elevations in their rHR compared to the GNE group. However, the mean SBP in the JOHD group was significantly decreased in the patients with JOHD compared to the GNE group. The mean DBP was lower in the JOHD group as well, but the results did not reach statistical significance (Table 2).


DBP, diastolic blood pressure; JOHD, juvenile-onset Huntington's Disease; rHR, resting heart rate; SBP, systolic blood pressure; SE, standard error.

The mean rHR of participants with adolescent-onset JOHD (87.79 ± 3.72 bpm) was significantly elevated compared to the GNE group (78.50 ± 0.83 bpm; *t* = 2.44, *p* = 0.016). The childhood-onset JOHD group had a mean rHR of 89.12 ± 3.11 bpm, which was also significantly elevated relative to the GNE group (*t* = 3.27, *p* = 0.001). The childhood-onset and adolescent-onset JOHD groups did not differ significantly from one another (*p* = 0.786) (Figure 1a). The mean SBP of participants with adolescent-onset JOHD was 111.79 ± 3.14 mmHg compared to 116.00 ± 0.71 in the GNE group (*t* = −1.30, *p* = 0.195). There was a significant difference between the childhood-onset JOHD group and the GNE groups, though. Specifically, the childhood-onset group's mean SBP was 108.66 ± 2.63 mmHg (*t* = −2.66, *p* = 0.0084). The difference between the childhood-onset and adolescent-onset groups was not statistically significant (*p* = 0.451) (Figure 1b). The mean DBP of the GNE group was 64.26 ± 0.43 mmHg. The adolescent-onset group's mean DBP was lower (63.11 ± 1.84 mmHg) compared to the GNE group, but not significantly so (*t* = -0.609, *p* = 0.543). However, the childhood-onset JOHD group's mean DBP was significantly lower (60.99 ± 1.55 mmHg) compared to the GNE group (*t* = −2.01, *p* = 0.045) (Figure 1c).

**Figure 1.** (**a**) Resting heart rate was significantly elevated in the adolescent-onset and childhood-onset JOHD groups compared to the GNE group. (**b**) Systolic BP was significantly decreased in the childhood-onset JOHD group compared to the GNE group. There was a gradual decrease in SBP from the GNE group to the adolescent-onset and childhood-onset JOHD groups. (**c**) Diastolic BP was significantly decreased in the childhood onset JOHD group compared to the GNE group. AO-JOHD: adolescent-onset JOHD; BP: blood pressure; Bpm: beats per minute; CO-JOHD: childhood-onset JOHD; GNE: gene-non-expanded group.
