Conversely, 5 immune cells—namely, CD16 on CD14‐CD16+ monocytes, CD25 on CD39+ secreting Treg cells, CD39+ resting Treg cells % CD4 Treg cells, CD4 on activated Treg cells and TCRgd % T cells—were found to negatively regulate the risk of developing delirium (OR < 1). This evidence concerns the gene CD4 and delirium.