Demographics, clinical characteristics, and neuropsychological test results
| aPD (n=24) | sPD (n=29) | p Value | |
| Age (y) | 65 (41–78) | 70 (45–84) | NS |
| Years of education | 8 (4–12) | 8 (6–12) | NS |
| Duration of disease (years) | 11 (3–18) | 5 (2–17) | 0.00 |
| Hoehn and Yahr stage | 3 (1–5) | 3 (1–3.5) | 0.01 |
| Side of predominant motor impairment (% right:% left) | 56.5:43.5 | 50:50 | NS |
| Sex distribution (% female:male) | 25:75 | 38:62 | NS |
| MMSE | 26 (15–30) | 28 (21–30) | NS |
| Premorbid IQ | 100.5 (69–136) | 100.5 (85–134) | NS |
| RBMT, immediate | 7 (1–22) | 7 (1–14) | NS |
| RBMT, long | 5 (0–18) | 6 (0–11) | NS |
| WLG | 17.5 (4–34) | 20.5 (5–33) | NS |
Values are medians (range); p values by Student'st test for independent samples (demographics); χ2 analysis (sex and side distributions), and Mann-Whitney U test (neuropsychological tasks); aPD=advanced Parkinson's disease with motor fluctuations; sPD=stable, non-fluctuating Parkinson's disease; MMSE= mini mental state examination; premorbid IQ=premorbid intelligence quotient; RBMT immediate=score of immediate story recall of the Rivermead behavioural memory test; RBMT long=score of long delay story recall of the RBMT; WLG=sum of both word list generation tasks.