Two hundred thirty-three patients with hip fracture were randomized to receive dexmedetomidine 0.1 µg/kg/h from 8 pm (pre-op night) to 8 am (day of surgery) (n=116) or identical-appearing saline (n=117). The primary outcome was POD incidence (3D-CAM) from postoperative day (POD) 1–7 or discharge. Secondary outcomes included preoperative sleep quality (LSEQ, ISI), delirium days, pain (NRS), C-reactive protein (CRP), patient-controlled analgesia presses, ADL at discharge, hospital stay, and adverse events. Outcomes were assessed through POD7/discharge, with twice-daily delirium assessments starting POD1. Overall, the results revealed lower POD with dexmedetomidine (10.3%) vs placebo and better preoperative sleep plus lower postoperative CRP, while other secondary endpoints were similar. These findings suggest that a single pre-op night of low-dose dexmedetomidine may be a practical strategy to prevent POD without increasing common adverse events.