Associations between Aβ40, Aβ42, and tau and postoperative delirium in older adults undergoing cardiac surgery

Postoperative delirium is a significant complication in older adults undergoing cardiac surgery. This study investigated associations between serum amyloid beta (Aβ40, Aβ42), their ratio Aβ42/Aβ40 (AβR), and total tau (tTau) and postoperative delirium.

This analysis included participants aged ≥ 60 years undergoing elective cardiac surgery with cardiopulmonary bypass. Serum Aβ40, Aβ42 and tTau were measured before surgery and on postoperative day one using a digital immunoassay. The primary outcome was postoperative delirium, assessed twice daily for 3 days using the Confusion Assessment Method.

Postoperative delirium developed in 12% (38/312) of participants. In adjusted analyses examining preoperative biomarkers, the odds of postoperative delirium were independently associated with Aβ40 (OR 1.44 per standard deviation increase, 95% CI 1.06-1.98; p = 0.021), AβR (OR 0.65, 95% CI 0.42-0.99; p = 0.046), and tTau (OR 1.65, 95% CI 1.01-2.68; p = 0.045). Aβ42 was statistically significant only in unadjusted analyses (OR 1.43, 95% CI 1.00-1.88; p = 0.012). In adjusted analyses examining postoperative biomarkers, the odds of postoperative delirium were independently associated with Aβ42 (OR 1.60, 95% CI 1.08-2.37; p = 0.020) and tTau (OR 1.56, 95% CI 1.09-2.23; p = 0.015).

Aβ40, AβR, and tTau were associated with postoperative delirium in elderly patients undergoing elective cardiac surgery. These findings suggest that postoperative delirium may be linked to pre-existing vulnerabilities shared with neurodegenerative processes along the Alzheimer's disease spectrum, offering new insights into its underlying mechanisms and potential connection to long-term cognitive decline.