Table 3.

Association between the biological measures and age after being adjusted for cognitive and/or motor scores in the control and PD groups

Groups	Dependent variable (Independent variable)		IGF‐1 (ng/mL)	cGP (ng/mL)	cGP/IGF‐1 molar ratio	IGFBP‐3 (ng/mL)	IGF‐1/IGFBP‐3 molar ratio
Control	Age (MoCA) n = 23	B	−0.01	0.39	0.96	−0.003	22.83
		P	0.53	0.02 *	0.04 *	0.12	0.46
	Age (Global Z score) n = 23	B	−0.02	0.16	0.38	−0.002	−4.61
		P	0.35	0.43	0.50	0.27	0.88
	Age (LMD) n = 23	B	−0.02	0.12	0.27	−0.002	−4.49
		P	0.42	0.54	0.63	0.37	0.88
PD‐N	Age (MoCA & MDS‐UPDRS III) n = 70	B	−0.03	0.29	1.57	−0.001	−26.47
		P	0.01 *	0.09	0.004 **	0.55	0.052
	Age (Global Z score & MDS‐UPDRS III) n = 67	B	−0.03	0.36	1.77	−0.002	−19.57
		P	0.02 *	0.05	0.002 **	0.25	0.17
	Age (LMD & MDS‐UPDRS III) n = 67	B	−0.03	0.37	1.84	−0.002	−21.00
		P	0.02 *	0.04 *	0.001 **	0.21	0.13
PD‐MCI	Age (MoCA & MDS‐UPDRS III) n = 63	B	−0.02	0.28	1.13	−0.001	−15.85
		P	0.17	0.12	0.06	0.36	0.32
	Age (Global Z score & MDS‐UPDRS III) n = 61	B	−0.02	0.21	0.56	−0.001	−11.79
		P	0.24	0.20	0.26	0.40	0.45
	Age (LMD & MDS‐UPDRS III) n = 61	B	−0.02	0.18	0.50	−0.001	−13.94
		P	0.21	0.26	0.32	0.40	0.37
PD‐D	Age (MoCA & MDS‐UPDRS III) n = 22	B	0.003	−0.70	−3.56	0.001	−1.64
		P	0.90	0.04 *	0.003 **	0.65	0.95

PD‐N, Parkinson disease with normal cognitive function; PD‐MCI, Parkinson disease with mild cognitive impairment; PD‐D, Parkinson disease with dementia; MDS‐UPDRS III, Movement Disorder Society—Unified Parkinson's Disease Rating Scale III; MoCA, Montreal Cognitive Assessment; LMD, learning memory domain scores; Global Z score, global measure of cognitive function derived from comprehensive neuropsychological testing; B, unstandardized co‐efficiency.

^* P < 0.05; ^** P < 0.01 indicate significant correlation of age and biological measures.