Serum 5-hydroxytryptamine levels as biomarkers for motor dysfunction and depression in Parkinson’s disease patients

Table 1 A comparison of the clinically relevant variables between non-dyskinesia and dyskinesia groups, mean ± SD

Variable	Non-dyskinesia (n = 37)	Dyskinesia (n = 33)	t/χ2	P value
Gender (male/female)	19/18	15/18	χ2 = 0.31	0.578
Age (years)	69.00 ± 8.86	63.03 ± 10.34	t = 2.56	0.013a
Height (cm)	163.64 ± 7.55	162.46 ± 7.66	t = 0.65	0.520
Weight (kg)	63.11 ± 10.32	60.76 ± 11.47	t = 0.90	0.373
MMSE	22.97 ± 6.29	21.79 ± 6.98	t = 0.74	0.462
Age of onset (years)	63.43 ± 8.63	55.12 ± 10.72	t = 3.50	0.001b
Course of disease (years)	5.16 ± 3.61	7.97 ± 3.97	t = -2.96	0.004b
UPDRS I (off phase)	2.70 ± 2.83	4.39 ± 3.94	t = -2.00	0.050a
UPDRS III (off phase)	42.62 ± 19.85	52.06 ± 20.87	t = -1.95	0.056
H-Y stage (off phase)	2.41 ± 0.90	2.97 ± 0.98	t = -2.45	0.017a
Duration of dopaminergic treatment (years)	3.12 ± 3.22	7.33 ± 4.14	t = -4.74	< 0.001c
Onset-to-treatment interval (years)	1.37 ± 2.79	0.53 ± 1.22	t = 1.59	0.117
Duration of wearing-off (months)	1.78 ± 6.46	19.70 ± 21.21	t = -4.45	< 0.001c
Duration of on-off (months)	1.46 ± 4.78	21.49 ± 29.21	t = -3.69	< 0.001c
Equivalent dose for wearing-off (mg)	40.54 ± 132.73	428.03 ± 326.96	t = -6.23	< 0.001c
Equivalent dose for on-off (mg)	47.30 ± 149.98	393.94 ± 306.12	t = -5.92	< 0.001c
Maximum daily levodopa (mg)	409.67 ± 294.09	735.39 ± 277.80	t = -4.78	< 0.001c

^aP < 0.05.

^bP < 0.01.

^cP < 0.001.

MMSE: Mini-Mental State Examination; UPDRS: Unified Parkinson’s Disease Rating Scale; H-Y: Hoehn-Yahr.

Table 2 Depression prevalence and clinical characteristics, mean ± SD

Indicator	Depression (n = 31)	Non-depression (n = 39)	t/χ2/r	P value
Depression cases	31	39	9.42	0.002a
HAM-D	18.5 ± 4.8	8.2 ± 3.1	6.85	< 0.001b
BDI-II	19.1 ± 5.0	7.9 ± 2.8	7.10	< 0.001b
PDQ-39 total	52.3 ± 15.7	28.4 ± 12.1	7.37	< 0.001b
PDQ-39 emotional well-being	68.2 ± 18.3	22.1 ± 14.6	11.82	< 0.001b
Correlation with disease duration	0.412	0.180	0.412	0.001a
Correlation with UPDRS I	0.689	0.250	0.689	< 0.001b
Correlation with UPDRS III	0.186	0.120	0.186	0.124
Correlation with H-Y stage	0.203	0.095	0.203	0.089

^aP < 0.01.

^bP < 0.001.

HAM-D: Hamilton Depression Rating Scale; BDI-II: Beck Depression Inventory II; PDQ-39: Parkinson’s Disease Questionnaire 39; UPDRS: Unified Parkinson’s Disease Rating Scale; H-Y: Hoehn-Yahr.

Table 3 Correlation analysis between 5-hydroxytryptamine levels and clinical variables

Variable	r	P value
Disease duration	-0.358	0.002b
H-Y staging	-0.312	0.008b
UPDRS I	-0.445	< 0.001c
UPDRS III	-0.267	0.025a
Duration of dopaminergic treatment	-0.389	0.001b
Duration of wearing-off episodes	-0.512	< 0.001c
Duration of on-off phenomena	-0.478	< 0.001c
Maximum daily levodopa dose	-0.334	0.005b
Age at disease onset	0.298	0.012a
Current age	0.156	0.196
PDQ-39 total score	-0.567	< 0.001c
PDQ-39 emotional well-being	-0.612	< 0.001c

^aP < 0.05.

^bP < 0.01.

^cP < 0.001.

H-Y: Hoehn-Yahr; UPDRS: Unified Parkinson’s Disease Rating Scale; PDQ-39: Parkinson’s Disease Questionnaire 39.

Table 4 Multivariate analysis and risk factors

Endpoint	Variable	OR	95%CI	P value	AUC 95%CI
Dyskinesia	Age at onset	0.921	0.867-0.979	0.009	0.867 (0.785-0.949)
	Duration of dopaminergic treatment	1.298	1.112-1.515	0.001
	Maximum daily levodopa dose	1.003	1.001-1.005	0.008
	Serum 5-HT level	0.984	0.975-0.993	0.001
Depression	H-Y staging	2.156	1.234-3.767	0.007	0.823 (0.731-0.915)
	UPDRS I	1.387	1.178-1.632	0.001
	Disease duration	1.142	1.012-1.289	0.031
	Serum 5-HT level	0.981	0.971-0.991	0.001

5-HT: 5-hydroxytryptamine; H-Y: Hoehn-Yahr; UPDRS: Unified Parkinson’s Disease Rating Scale; OR: Odds ratio; CI: Confidence interval; AUC: Area under the curve.