As the control group was significantly younger than the AD group in both studies (see Table 1), we also tested for a correlation between CSF Ng and age, but no such association was found in the paired cohort (AD group: P = 0.667, rs = −0.1; control group: P = 0.11, rs = −0.37) or in the validation study (AD group: P = 0.258, rs = 0.34; control group: P = 0.77, rs = −0.08). Here, NRGN is linked to Alzheimer disease.