Advanced age, male sex, anemia, diabetes, COPD, coronary heart disease, arrhythmia, congestive heart failure, chronic kidney disease, cerebrovascular accident, surgery over 48 h after injury or admission, lower preoperative serum hemoglobin or ALB levels, lower partial pressure of oxygen in arterial blood, and higher BUN or alanine aminotransferase levels might contribute to the development of POP after hip fracture surgery. The gene discussed is ALB; the disease is cardiac arrhythmia.