BDNF and Alzheimer disease: In addition, the levels of NDEV total tau and plasma TNF-α were positively correlated in AD cases (r = 0.254, p < 0.01), and NDE Aβ42 and P-T181-tau showed significant negative correlations with serum BDNF (r = –274 and r = –250, respectively, p < 0.05) in patients with mild-to-moderate AD.