This study will use group-based trajectory modeling to identify the different postoperative pain trajectory groups that exist in a mixed surgical population (non-cardiac surgery) of elderly patients during the first seven days after surgery. The aim of this study is to explore the diversity in the development of postoperative pain among elderly patients and to identify the risk factors for acute pain trajectory after surgery by investigating demographic, psychological, and clinical variables. The predictive effect of different trajectories of early postoperative acute pain on postoperative chronic pain will also be explored.