Brendan Silbert, Lisbeth Evered, David A Scott

Centre for Anaesthesia and Cognitive Function, Department of Anaesthesia, St. Vincent's Hospital, Melbourne, Australia

Background: The plasma protein apolipoprotein E (APOE) is a risk factor for degenerative cognitive decline manifested by mild cognitive impairment (MCI) and later by Alzheimer's Disease (AD). Patients undergoing coronary artery bypass (CABG) surgery are known to have a high prevalence of preoperative cognitive impairment (PreCI) and postoperative cognitive dysfunction (POCD). Since both MCI and AD generally occur in the elderly, the same age group who commonly present for CABG surgery, we investigated if the APOE e4 was associated with patients manifesting PreCI and POCD. Results from previous studies have been equivocal.^1,2

Methods: The plasma of 282 patients who had undergone neuropsychological testing before and 3 and 12 months after surgery CABG surgery, was analyzed for APOE genotype. Patients were classified as having PreCI if cognitive function was decreased in two or more tests compared to a healthy control group and POCD was defined as a decrease in two or more tests compared to the group mean baseline score.

Results: The APOE e4 allele was found in 83 patients. Although PreCI was present in 105 (37.2%) patients and POCD present in 33 (12%) and 31 (11%) at 3 and 12 months postoperatively, there was no relationship to either the presence of the APOE e4 allele or any of the 6 genotypes.

Conclusions: PreCI and POCD are not associated with APOE e4 genotype suggesting that cognitive impairment both before and after CABG surgery may not be associated with degenerative cognitive decline.

References

1. Steed L, Kong R, et al. The role of apolipoprotein E in cognitive decline after cardiac operation. Ann Thorac Surg 2001; 71: 823-6.
2. Tardiff BE, Newman MF,et al. Preliminary report of a genetic basis for cognitive decline after cardiac operations. Ann Thorac Surg 1997; 64: 715-20.