MMP9 and Alzheimer disease: Interestingly, the cognitively healthy individuals with risk markers for future AD, i.e. AD-supportive CSF biomarker levels of T-tau, P-tau and Aβ42 or the presence of the APOE ε4 allele, had higher CSF MMP-3 and MMP-9 levels and higher CSF MMP-3/TIMP-1 ratios compared to the healthy individuals without risk markers.