Can the prediction model using regression with optimal scale improve the power to predict the Parkinson's dementia?

Table 1 Measurement of variables

Factors	Measurement	Characteristics
Demographic factors	Sex	Male or female
	Age	60-74, 75+
	Mainly used hand	Left hand or right hand
	Education level	Middle school graduate and below or high school graduate and above
Family history of the disease	Parkinson's disease; Alzheimer's disease	Yes or no; Yes or no
Health behaviors	Pack-years (smoking)	Non-smoking, 1-20, 21-40, 41-60, or ≥ 61 pack-years
	Coffee-drinking	Yes or no
	Mean coffee intake per day (cups/d)	No, ≤ 1, 2-3, or ≥ 4 cups
	Coffee drinking period (yr)	No, ≤ 5, 6-9, or ≥ 10
Disease history	Carbon monoxide poisoning	Yes or no
	Diabetes	Yes or no
	Alcoholism	Yes or no
	Hyperlipidemia	Yes or no
	Traumatic brain injury	Yes or no
	Hypertension	Yes or no
Exercise characteristics related to Parkinson's disease relatedmotor signs	Tremor	Yes or no
	Rigidity	Yes or no
	Akinesia/bradykinesia	Yes or no
	Postural instability	Yes or no
	Late motor complications	Yes or no
Neuropsychological test	K-MoCA	Continuous variable
	K-MMSE	Continuous variable
	Global CDR score	Continuous variable
	Sum of boxes in CDR	Continuous variable
	Hoehn and Yahr staging	Continuous variable
	UPDRS (Total UPDRS score)	Continuous variable
	UPDRS (Motor UPDRS score)	Continuous variable
	K-IADL	Continuous variable
	Schwab and England ADL	Continuous variable

K-MoCA: Korean version of montreal cognitive assessment; K-MMSE: Korean version of mini mental state examination; CDR: Clinical dementia rating; UPDRS: Untitled parkinson disease rating; K-IADL: Korean version of instrumental activities of daily living; Schwab and England ADL: Schwab and England avtivities of daily living scale.

Table 2 General characteristics of the subjects based on Parkinson's disease with dementia, n (%)

Variables	PD-MCI (n = 179)	PDD (n = 110)	P value
Age			0.168
60-74	117 (65.0)	63 (35.0)
75+	62 (56.9)	47 (43.1)
Sex			0.550
Male	78 (63.9)	44 (36.1)
Female	101 (60.5)	66 (39.5)
Education level			0.072
Middle school graduate and below	110 (58.2)	79 (41.8)
High school graduate and above	69 (69.0)	31 (31.0)
Family history of the Parkinson's disease			0.600
No	144 (64.3)	80 (35.7)
Yes	12 (70.6)	5 (29.4)
Family history of the Alzheimer's disease			0.285
No	130 (63.4)	75 (36.6)
Yes	8 (80.0)	2 (20.0)
Carbon monoxide poisoning			0.743
No	158 (62.5)	95 (37.5)
Yes	10 (66.7)	5 (33.3)
Traumatic brain injury			0.277
No	158 (62.0)	97 (38.0)
Yes	10 (76.9)	3 (23.1)
Diabetes			0.508
No	144 (64.0)	81 (36.0)
Yes	35 (59.3)	24 (40.7)
Hypertension			0.304
No	110 (65.5)	58 (34.5)
Yes	69 (59.5)	47 (40.5)
Hyperlipidemia			0.220
No	155 (61.8)	96 (38.2)
Yes	24 (72.7)	9 (27.3)

Table 3 Results of the neuropsychological profiles

Results	K-MMSE	K-MoCA	Global CDR score	Sum of boxes in CDR	K-IADL	Total UPDRS	Motor UPDRS	H&Y staging	ADL
Mean	22.73	16.27	0.67	2.80	1.90	43.56	25.33	2.45	74.40
Standardized mean error	0.32	0.44	0.03	0.22	0.26	2.02	0.77	0.04	1.42
Standard deviation	5.51	6.33	0.56	3.49	4.08	23.77	12.59	0.78	18.30
Minimum	3	0	0	0	0	0.18	2.0	1.0	10
Maximum	30	27	4.0	25.0	28.0	130.00	74.0	5.0	100

K-MoCA: Korean version of montreal cognitive assessment; K-MMSE: Korean version of mini mental state examination; CDR: Clinical dementia rating; UPDRS: Untitled parkinson disease rating; H&Y staging: Hoehn and Yahr staging; K-IADL: Korean version of instrumental activities of daily living; Schwab and England ADL: Schwab and England avtivities of daily living scale.

Table 4 Result of the neuropsychological profiles based on Parkinson's disease with dementia, mean ± SD

Variables	PD-MCI (n = 179)	PDD (n = 110)	P value
K-MMSE	24.3 ± 3.4	18.8 ± 5.6	< 0.001
K-MoCA	19.4 ± 4.9	11.9 ± 5.4	< 0.001
CDR (sum of boxes)	1.6 ± 1.4	5.1 ± 4.9	< 0.001
K-IADL	1.3 ± 2.9	3.0 ± 5.4	0.001
UPDRS (Total UPDRS score)	36.4 ± 17.9	56.1 ± 27.2	< 0.001
UPDRS (Motor UPDRS score)	22.6 ± 10.1	29.4 ± 14.6	< 0.001
H&Y staging	2.2 ± 0.6	2.7 ± 0.8	0.001
Schwab and England ADL	80.0 ± 14.4	65.6 ± 19.8	< 0.001

K-MoCA: Korean version of montreal cognitive assessment; K-MMSE: Korean version of mini mental state examination; CDR: Clinical dementia rating; UPDRS: Untitled parkinson disease rating; H&Y staging: Hoehn and Yahr staging; K-IADL: Korean version of instrumental activities of daily living; Schwab and England ADL: Schwab and England avtivities of daily living scale.

Table 5 Results of regression with optimal scale

Test	b	SE by boost 1	df	F	P value
K-MMSE	-0.522	0.168	2	9.684	< 0.001
KMoCA	-0.206	0.238	3	0.750	0.527
CDR (Global CDR score)	0.127	0.269	1	0.222	0.639
CDR (sum of boxes)	-0.271	0.412	3	0.431	0.732
K-IADL	0.237	0.224	2	1.119	0.334
UPDRS (Total UPDRS score)	0.433	0.444	3	0.949	0.423
UPDRS (Motor UPDRS score)	-0.338	0.330	3	1.045	0.380
H&Y staging	0.440	0.197	3	5.008	0.004
Schwab and England ADL	0.353	0.333	2	1.123	0.333

The regression model was adjusted for demographic factors, family disease history, health behaviors, disease history, Parkinson's disease-related motor signs and neuropsychological test. 1 SE by boost: Standard error by bootstrap (with n = 1000); K-MoCA: Korean version of montreal cognitive assessment; K-MMSE: Korean version of mini mental state examination; CDR: Clinical dementia rating; UPDRS: Untitled parkinson disease rating; H&Y staging: Hoehn and Yahr staging; K-IADL: Korean version of instrumental activities of daily living; Schwab and England ADL: Schwab and England avtivities of daily living scale.

Table 6 Quantification index of Korean version of mini mental state examination

Category (point)	Quantification index
3-14	-1.260
15-18	-1.198
19-20	-1.013
21-22	-.706
23-24	-.320
25	0.135
26	0.656
27	1.183
28	1.508
29-30	1.616

Table 7 Quantification index of Hoehn and Yahr staging

Category (point)	Quantification index
1.0	-2.787
1.5	-0.609
2.0	-0.187
2.5	-0.081
3.0	0.151
4.0	1.179
5.0	2.167

Table 8 Optimal classification scores: odds ratios and 95% confidence interval

Optimal classification scores	B	SE	Wald	P value	OR (95%CI)
K-MMSE 25+ (Ref)			69.856	< 0.01
23-24	1.499	0.473	10.035	0.002	4.478 (1.77-11.32)
21-22	2.731	0.494	30.522	< 0.01	15.345 (5.82-40.43)
19-20	2.587	0.549	22.195	< 0.01	13.294 (4.53-39.00)
15-18	3.111	0.505	37.937	< 0.01	22.441 (8.33-60.39)
3-14	4.008	0.799	25.185	< 0.01	55.020 (11.50-263.19)
H&Y staging 1.0-2.5 (Ref)
3.0-5.0	1.110	0.350	10.079	0.001	3.035 (1.52-6.02)

K-MMSE: Korean version of mini mental state examination; H&Y staging: Hoehn and Yahr staging.