Our results suggest that further investigations should be undertaken to understand whether increasing the relative levels of shorter Aβ peptides such as Aβ38 is in fact an effective strategy to treat AD.42,43 We must note that we did not test whether CSF Aβ38 has added clinical value over well-established biomarkers of amyloid, tau, and neurodegeneration. Here, MAPT is linked to Alzheimer disease.