MAPT and delirium: Its levels increase in response to various neurodegenerative conditions and following stroke.29,30 Elevated Tau protein levels can also result from injury, synaptic activity, or synaptic pruning, making their interpretation complex.31 Plasma Tau protein levels have been linked to the incidence and severity of postoperative delirium.24 To our knowledge, this study is the first to demonstrate an association between Tau protein levels and SAD.