NEFL and Alzheimer disease: Our findings contrast with Grøndvedt et al., who reported a positive association of CSF sαKl with CSF Aβ42 and a negative association with CSF T-tau and P-tau, while plasma sαKl only correlated negatively with CSF T-tau and P-tau.4 Ren et al. observed a negative correlation between plasma Klotho and CSF Aβ42, but not any of the other investigated CSF biomarkers (T-tau, P-tau181, NfL) in a mixed sample of cognitively unimpaired individuals and AD patients,24 suggesting that higher sαKl levels are associated with greater Aβ accumulation and potentially more advanced AD pathology.