Based on the current literature, we focused on specific single nucleotide polymorphisms (SNPs) of four candidate genes associated with reduced rates or acceleration of cognitive impairment but never studied in delirium: (1) KIdney and BRAin expressed protein (KIBRA; rs17070145; C/T), (2) KLOTHO (rs9536314; T/G), (3) Sirtuin 1 (SIRT1; rs7896005; A/G), and (4) FK506 binding protein 51 (FKBP5; rs1360780; C/T). This evidence concerns the gene KL and delirium.