Table 2.

Correlations among kynurenine, tryptophan kynurenine/tryptophan in CSF and serum correlated (rho), by age and gender.

	Kynurenine CSF (μM)	Tryptophan CSF (μM)	Kynurenine/Tryptophan CSF	Kynurenine serum (μM)	Tryptophan serum (μM)	Kynurenine/Tryptophan serum	Age	Gender (women/men)
Kynurenine CSF (μM)		0.522	0.496	0.614	-0.003	0.576	0.471	0.168
		p < 0.001	p < 0.001	p < 0.001	p = 0.982	p < 0.001	p < 0.001	p = 0.150
Tryptophan CSF (μM)			-0.356	0.162	0.207	-0.001	0.268	0.351
			p = 0.002	p = 0.166	p = 0.074	p = 0.993	p = 0.020	p = 0.002
Kynurenine/Tryptophan CSF				0.584	-0.136	0.650	0.309	-0.035
				p < 0.001	p = 0.244	p < 0.001	p = 0.007	p = 0.764
Kynurenine serum (μM)					0.298	0.682	0.470	0.254
					p = 0.009	p < 0.001	p < 0.001	>p = 0.028
Tryptophan serum (μM)						-0.423	0.022	0.383
						p < 0.001	p = 0.849	p = 0.001
Kynurenine/Tryptophan serum							0.448	-0.063
							p < 0.001	p = 0.592
Age								0.138
								p = 0.218
Gender (women/men)

Kynurenine in serum and CSF is highly correlated with each other. Kynurenine in CSF is significantly correlated with age, but not with gender. Kynurenine in serum is significantly correlated with age and gender. Tryptophan in serum is significantly correlated with gender but not age. Men have higher values on both kynurenine and tryptophan in serum. Thus, only Kynurenine seems to be related to age. Only serum values of Kynurenine and Tryptophan are significantly related to gender. Kynurenine/tryptophan in CSF and serum correlated highly with each other, and showed also positive correlations with age but not with gender.