Background Delirium, or a disturbance of consciousness and a change in cognition that develop over a short period of time, (1) complicates 2.6 million hospitalizations among U.S. adults aged 65 or older each year. (2,3) Patients who experience delirium during hospitalization face increased risks morbidity, mortality, and functional disability. (4) Each year, delirium accounts for $6.9 billion in Medicare hospital expenditures. (5) Delirium occurs in 35% to 65% of the 320,000 older U.S. adults hospitalized for hip fracture each year. (6) While adverse survival and functional outcomes are common after hip fracture, (7) a single episode of delirium doubles the odds of both new functional dependence and new ambulatory disability at six months after fracture, and triples the odds of death or new nursing home placement. (8) Compared to general endotracheal anesthesia, spinal anesthesia may decrease the incidence of postoperative delirium after hip fracture surgery. Small randomized trials of anesthesia type for hip fracture have suggested a 50% lower risk of acute confusion after hip fracture surgery with spinal anesthesia, (9) but the heterogeneity of outcome definitions and measurement strategies employed by past trials, along with their use of historical anesthesia practices limit their applicability to current practice.