Frailty as a mediator of postoperative delirium in older adults undergoing orthopedic surgery: A causal mediation analysis

Background

Postoperative delirium has a high prevalence in hospitalized older adults. Frail older adults have an increased risk for developing it. Preoperative pain—a common symptom in older adults with orthopedic conditions—shows a connection with frailty through an inflammatory process. However, an association among preoperative pain, frailty, and postoperative delirium remains unexplored among older adults undergoing orthopedic surgery.

Objectives

To examine the magnitude, direction, and mediation effect of frailty on the association between preoperative pain and postoperative delirium among older adults undergoing orthopedic surgery.

Design

A secondary analysis of a prospective cohort study.

Setting and participants

A cohort of 200 older adults (60 years and older) who underwent major orthopedic surgery at a university hospital in Thailand was recruited for the study.

Methods

Participants responded to the Demographic and Health Information Form, the Reported Edmonton Frailty Scale-Thai version, and the Thai version of the 4 A's test. Analyses were conducted using a causal mediation analysis with 95 % confidence intervals.

Results

We found that 12.5 % of participants developed postoperative delirium. For the direct paths associated with postoperative delirium, statistically significant effects were observed for frailty, preoperative pain, and comorbidity. Considering frailty as a mediator of postoperative delirium, a significant positive indirect effect was identified from preoperative pain. Controlling for age and comorbidities, frailty mediated the association between preoperative pain and postoperative delirium in a statistically significant manner; the average direct effect was 0.014 (95 % confidence interval: 0.008–0.020), the average causal mediating effect was 0.002 (95 % confidence interval: 0.000–0.010), the total effects was 0.017 (95 % confidence interval: 0.010–0.020), and the probability mediation accounted for 14 % (95 % confidence interval: 0.031–0.300).

Conclusion

Integrating the concept of age-related decline and frailty assessment may offer opportunities to provide disease-specific care and strengthen precision perioperative care, which ultimately enhance quality of life in older adults undergoing orthopedic surgery.