Postoperative cognitive dysfunction and its relationship to cognitive reserve in elderly total joint replacement patients

Whether total joint replacement (TJR) patients are susceptible to postoperative cognitive dysfunction (POCD) remains unclear due to inconsistencies in research methodologies. Moreover, cognitive reserve may moderate the development of POCD after TJR, but has not been investigated in this context. The current study investigated POCD after TJR, and its relationship with cognitive reserve, using a more rigorous methodology than has previously been utilized. Fifty-three older adults (aged 50+) scheduled for TJR were assessed pre and post surgery (6 months). Forty-five healthy controls matched for age, gender, and premorbid IQ were re-assessed after an equivalent interval. Cognition, cognitive reserve, and physical and mental health were all measured. Standardized regression-based methods were used to assess cognitive changes, while controlling for the confounding effect of repeated cognitive testing. TJR patients only demonstrated a significant decline in Trail Making Test Part B (TMT B) performance, compared to controls. Cognitive reserve only predicted change in TMT B scores among a subset of TJR patients. Specifically, patients who showed the most improvement pre to post surgery had significantly higher reserve than those who showed the greatest decline. The current study provides limited evidence of POCD after TJR when examined using a rigorous methodology, which controlled for practice effects. Cognitive reserve only predicted performance within a subset of the TJR sample. However, the role of reserve in more cognitively compromised patients remains to be determined.