Accordingly, we determined the concentrations of p75NTR-ECD in the serum of four groups of subjects including an AD group, Parkinson disease (PD) group (as a neurodegeneration disease control), an acute ischemic stroke group (as a cerebrovascular disease control) and age-matched elderly controls without neurologic disorders (EC), as well as the concentrations of CSF p75NTR-ECD in a subset within the AD and EC groups. This evidence concerns the gene NGFR and nervous system disorder.