INS and Hyperglycemia: Of these, 9,572 (35.4%) patients were defined as having preoperative hyperglycemia (FPG ≥ 7 mmol/L), 8,746 (32.4%) were aged ≥ 65 years old, 15,630 (57.9%) were males, 1,459 (5.4%) had a history of ischemic stroke, 13,822 (51.1%) were under insulin medication, 2,319 (8.6%) received neurosurgery, and 10,431 (38.6%) underwent a surgery length exceeding 3 h.