MAPT and nervous system disorder: Our study showed that the elevated CSF Aβ42, Aβ42/T-tau, and Aβ42/P-tau may be protective factors for POD in the patients, which can predict the occurrence of POD, and Aβ42 may be the major component of senile plaques in some Neurological disorders, as we mentioned POD in this study and the study of AD in Selkoe and Hardy (2016).