Table 3

Change scores, relative changes and effect sizes for matched cohorts

Change scoreRelative change (%)Effect size
STN-DBSMEDSTN-DBSMEDCohen’s dClassification
PDQ-8 SI6.1–6.221.0–20.90.72Moderate
SCOPA-motor examination2.8–0.525.7–4.10.67Moderate
SCOPA-activities of daily living0.6–1.39.4–18.10.56Moderate
SCOPA-motor complications1.5–0.763.9–20.60.85Large
NMSS total score15.6–16.828.8–36.51.11Large
 Perceptual problems/hallucinations0.1–0.69.1–61.00.24Small
 Sexual function2.00.666.712.30.25Small
  • Change scores and relative changes from baseline to 36-month follow-up in the STN-DBS and MED groups. Effect sizes of the between-group comparison STN-DBS versus MED (Mann-Whitney U test).

  • Change score = (mean testbaseline − mean test follow-up)

  • Relative change = (mean testbaseline − mean testfollow-up) / mean test baseline x 100.

  • Cohen’s d = (mean pre-post changetreatment group − mean pre-post changecontrol group) / SD pretestpooled groups.

  • Cohen’s d can be classified as ‘small’ (0.20≥d<0.50), ‘moderate’ (0.50≥d<0.80) and ‘large’ (d≥0.80).

  • Effect size for the NMSS cardiovascular domain was favourable in the MED group and for all other outcome parameters and NMSS groups in the STN-DBS group.

  • LEDD, levodopa equivalent daily dose; MED, standard-of-care medical treatment; NMSS, Non-motor Symptom Scale; PDQ-8 SI, 8-item Parkinson’s Disease Questionnaire Summary Index; SCOPA, Scales for Outcomes in Parkinson’s disease; STN-DBS, subthalamic nucleus deep brain stimulation.