MMP9 and Alzheimer disease: Cognitively healthy individuals with risk markers for future Alzheimer’s disease, i.e., critical CSF biomarker levels of T-tau, P-tau and Abeta42, or the presence of the APOE epsilon4 allele, have higher CSF MMP-3 and MMP-9 levels and higher CSF MMP-3/TIMP-1 ratios compared to the healthy individuals without risk markers [257].