Development of a depression in Parkinson's disease prediction model using machine learning

Table 1 General characteristics of the subjects with depression, n (%)

Characteristics	Depression		P value
	No (n = 130)	Yes (n = 93)
Age			0.918
60-74 yr	83 (58.0)	60 (42.0)
≥ 75 yr	47 (58.8)	33 (41.3)
Sex			0.183
Male	62 (63.3)	36 (36.7)
Female	68 (54.4)	57 (45.6)
Education level			0.158
Middle school graduate and below	76 (54.7)	63 (45.3)
High school graduate and above	54 (64.3)	30 (35.7)
Handness			0.905
Right	125 (58.4)	89 (41.6)
Left	2 (66.7)	1 (33.3)
Both hands	2 (50.0)	2 (50.0)
Family PD history			0.921
No	108 (58.7)	76 (41.3)
Yes	9 (60.0)	6 (40.0)
Pack year (smoking)			0.666
1-20 pack year	6 (42.9)	8 (57.1)
21-40 pack year	5 (62.5)	3 (37.5)
41-60 pack year	1 (50.0)	1 (50.0)
61+ pack year	118 (59.3)	81 (40.7)
Traumatic brain injury			0.852
No	118 (60.8)	76 (39.2)
Yes	7 (63.6)	4 (36.4)
Diabetes			0.214
No	103 (60.9)	66 (39.1)
Yes	25 (51.0)	24 (49.0)
Hypertension			0.246
No	71 (55.5)	57 (44.5)
Yes	57 (63.3)	33 (36.7)
Hyperlipidemia			0.220
No	114 (60.3)	75 (39.7)
Yes	14 (48.3)	15 (51.7)
Tremor			0.630
No	17 (54.8)	14 (45.2)
Yes	107 (59.4)	73 (40.6)
Rigidity			0.342
No	8 (72.7)	3 (27.3)
Yes	120 (58.3)	86 (41.7)
Bradykinesia			0.962
No	7 (58.3)	5 (41.7)
Yes	121 (59.0)	84 (41.0)
Postural instability			0.187
No	66 (64.1)	37 (35.9)
Yes	59 (55.1)	48 (44.9)
REM and RBD			0.081
No	58 (63.7)	33 (36.3)
Yes	55 (51.4)	52 (48.6)
Late motor complications			0.140
Only ON-OFF/Wearing OFF	12 (54.5)	10 (45.5)
Only levodopa-induced dyskinesia	2 (22.2)	7 (77.8)
Both ON-OFF/Wearing OFF and levodopa-induced dyskinesia are present	13 (59.1)	9 (40.9)
Both ON-OFF / Wearing OFF and levodopa-induced dyskinesia are absent	99 (61.1)	63 (38.9)
K-MMSE, mean ± SD	24.2 ± 4.6	21.5 ± 6.1	< 0.001
K-MoCA, mean ± SD	18.2 ± 6.1	13.9 ± 6.7	< 0.001
Global CDR score, mean ± SD	0.5 ± 0.3	0.8 ± 0.7	< 0.001
Sum of boxes in CDR, mean ± SD	2.3 ± 3.1	3.3 ± 4.0	0.041
K-IADL, mean ± SD	1.3 ± 3.0	3.2 ± 5.6	0.003
Total score of UPDRS, mean ± SD	34.5 ± 17.1	53.2 ± 26.1	< 0.001
Motor score of UPDRS, mean ± SD	22.7 ± 10.9	30.0 ± 13.5	< 0.001
H and Y staging, mean ± SD	2.2 ± 0.6	2.6 ± 0.9	0.002
Schwab and England ADL, mean ± SD	80.1 ± 14.5	67.3 ± 21.5	< 0.001

CDR: Clinical Dementia Rating; K-MMSE: Korean Mini-Mental State Examination; K-MoCA: Korean-Montreal Cognitive Assessment; K-IADL: Korean Instrumental Activities of Daily Living; UPDRS: Untitled Parkinson`s Disease Rating total score; H and Y: Hoehn and Yahr; ADL: Activities of Daily Living.

Table 2 Comparing the accuracy of depression in Parkinson's disease prediction model, %

Type of algorithm	Overall accuracy	Sensitivity	Specificity
C-SVM: Linear	92.5	92.0	93.3
C-SVM: Polynomial	70.0	100	20.0
C-SVM: Gaussian	87.5	96.0	73.3
C-SVM: Sigmoid	85.0	88.0	80.0
Nu-SVM: Linear	90.0	92.0	86.6
Nu-SVM: Polynomial	92.5	92.0	93.3
Nu-SVM: Gaussian	95.0	96.0	93.3
Nu-SVM: Sigmoid	82.5	92.0	66.6

SVM: Support vector machine.

Table 3 Functional weight (importance of variables)

Variables	Functional weight
K-MMSE	-1.454
K-MoCA	-4.499
CDR (Global CDR score)	2.643
CDR (sum of boxes)	2.607
K-IADL	4.919
Total UPDRS	5.302
Motor UPDRS	0.978
H and Y staging	-2.190
Schwab and England ADL	-5.055
Age (60-74)	-3.638
Age (75+)	3.638
Gender (female)	0.345
Education (high school graduate and above)	1.150
Family PD history (yes)	0.232
Pack year (21-40)	0.032
Pack year (41-60)	0.000
Pack year (61+)	-1.032
Coffee (yes)	1.006
Pesticide exposure (currently not exposed but exposed previously)	-1.000
Pesticide exposure (currently exposed to pesticide)	2.264
Tremor (yes)	0.000
Rigidity (yes)	-1.000
Bradykinesia (yes)	0.675
Postural instability (yes)	1.117
LMC (levodopa-induced dyskinesia)	3.000
LMC (Both Wearing OFF and levodopa-induced dyskinesia are present)	0.264
LMC (Both Wearing OFF and levodopa-induced dyskinesia are absent)	-4.715
REM sleep behavior disorders	1.261
Number of support vectors: 34

CDR: Clinical Dementia Rating; K-MMSE: Korean Mini-Mental State Examination; K-MoCA: Korean-Montreal Cognitive Assessment; K-IADL: Korean Instrumental Activities of Daily Living; UPDRS: Untitled Parkinson`s Disease Rating total score; H and Y: Hoehn and Yahr; ADL: Activities of Daily Living; REM: Rapid eye movement; PD: Parkinson's disease.