Table. Characteristics of the Study Sample^a.

		PD Groups
Variable	HCs (n=23)	PD-NC (n=61)	PD-MCI (n=12)	PDD (n=11)
Clinical and demographic
Age, y	71.5 (9.2)	69.3 (5.7)	75.7 (7.7)b	73.1 (7.2)
Male sex, No. (%)	5 (22)	39 (64)c	10 (83)	7 (64)
Education, y	15.8 (2.9)	16.0 (2.8)	15.2 (1.6)	14.4 (2.7)
PD duration, y	NA	7.1 (3.8)	9.3 (6.6)	9.0 (7.1)
Hoehn and Yahr stage, median (IQR)	NA	2.0 (2.0-2.5)	2.0 (2.0-3.0)	3.0 (2.5-3.0)d
Levodopa dosage, mg/de	NA	424 (368)	543 (441)	610 (209)
Dopamine agonist dosage, mg/de	NA	101 (164)	75 (145)	45 (101)
UPDRS motor score	NA	20.3 (8.9)	23.6 (11.1)	29.5 (12.7)
GDS-15 scoref	0.7 (1.4)	2.2 (2.3)g	3.3 (3.1)	4.0 (3.1)
Neuropsychological assessment
DRS-2
Total score	141.5 (2.5)	139.4 (3.0)h	127.8 (3.5)	108.5 (17.1)i
Total standardized score	13.2 (2.1)	11.5 (2.0)j	6.8 (0.9)	3.3 (1.2)k
Memory subscale	NA	23.7 (1.3)	20.5 (2.2)	16.4 (4.7)
Attention subscale	NA	36.2 (1.7)	34.9 (1.9)	33.1 (3.4)l
Conceptualization subscale	NA	37.3 (1.6)	35.3 (2.1)	31.8 (3.6)l,m
Initiation/perseveration subscale	NA	36.2 (1.7)	31.3 (3.9)	22.8 (6.9)n
Construction subscale	NA	5.9 (0.3)	5.9 (0.3)	4.4 (2.2)o
HVLT-Rp
Immediate recall	NA	21.0 (4.8)	13.4 (4.7)	11.7 (7.0)l,q
Delayed recall	NA	6.6 (3.0)	3.8 (2.5)	1.6 (2.1)l,r
Recognition discrimination	NA	10.0 (1.5)	8.3 (1.8)	6.3 (4.4)l

Abbreviations: DRS-2, Dementia Rating Scale–2; GDS-15,15-Item Geriatric Depression Scale¹⁶ (a commonly used version as opposed to the original 30-item GDS); HCs, healthy controls; HVLT-R, Hopkins Verbal Learning Test–Revised; IQR, interquartile range; NA, not applicable; PD, Parkinson disease; PDD, PD with dementia-level cognitive deficits; PD-MCI, PD with mild cognitive impairment; PD-NC, PD with normal cognition; UPDRS, Unified Parkinson’s Disease Rating Scale.

^aComparisons are between PD-NC and HC groups and among PD-NC, PD-MCI, and PDD groups. Unless otherwise indicated, data are expressed as mean (SD)

^bP= .01, PD-NC vs PD-MCI group (Tukey test).

^cP= .001, PD-NCvs HC group (${\chi }_1^2=11.9$).

^dP= .001, PDDvs PD-NC group (Tukey test)

^eIncludes 83 PD patients.

^fIncludes 102 PD patients and HCs.

^gP= .001, HCvs PD-NC group (t_67.1 = −3.6)

^hP= .005, PD-NC vs HC group (t₈₂ = 2.9).

ⁱP< .001 among all PD groups (F_2,81 = 105.6)

^jP= .001, PD-NC vs HC group (t₈₂ = 3.3).

^kP< .001 among all PD groups (F_2,81 = 114.9)

^lP< .001, PDD vs PD-NC group (Tukey test).

^mP = .03, PDDvs PD-MCI group (Tukeytest)

ⁿP< .001 among all PD groups (F_2,81 = 88.0).

^oP< .001, PDD vs PD-MCI group and PDD vs PD-NC group (Tukey test)

^pIncludes 60 PD patients.

^qP= .001, PD-NCvs PD-MCI group (Tukey test)

^rP= .03, PD-NC vs PD-MCI group (Tukey test).