Table 5.

Correlation between serum BDNF concentration and H-Y stage in patients with Parkinson’s disease controls (n = 120)

Variable	BDNF (correlation coefficient)	p value
H-Y stages I–V #	rs = 0.907	<0.001
H-Y stages 0–V #	rs = 0.008	0.927
H-Y stages 0–II #	rs = −0.387	<0.001
H-Y stages III–V #	rs = 0.481	0.096

Note: Controls were considered H-Y stage 0. The serum BDNF concentration was not correlated with stages 0–V, consistent with the following clinical condition: the serum BDNF concentration was higher in controls (H-Y stage 0), relatively lower in patients with the early stages of PD (stages I and II), and higher in patients with the advanced stages of PD (stages III–V).

BDNF = brain-derived neurotrophic factor, H-Y stage = Hoehn and Yahr stage

^#Spearman’s rank correlation coefficient (r_s)