MAPT and Alzheimer disease: Furthermore, Fong et al. found a relationship between CSF biomarkers for Alzheimer’s disease and POD in older adults, supported by the gradient effect, which indicates that when delirium occurs in individuals with any amyloid, tau, and neurodegeneration (ATN) biomarker, the severity of the delirium increases beyond the level of either delirium or ATN biomarkers alone [60].