INS and delirium: Prespecified subgroup analysis revealed an age-related response, with participants aged ≤88 years showing shorter delirium duration with intranasal insulin [n = 46; intranasal insulin: median 3.9 (IQR 2.9, 6.9) days vs control: 7.0 (4.7, 9.7); HR 0.34, 0.16-0.74; P = .006], whereas no difference was observed in participants aged >88 years [n = 51; intranasal insulin 5.4 (2.9, 11.1) vs control 4.9 (2.6, 12.9); HR 0.87, 0.39-1.94; P = .73].<h4>Conclusion and relevance</h4>This is the first study of intranasal insulin for delirium treatment.