When they compared delirium rates in relation to genotype, they found that 28.3% of the ApoE4 carriers with at least one allele experienced delirium, compared with 11.1% of patients who carried other ApoE alleles.
A multivariate analysis adjusted for other delirium risk factors -- including older age, change in postoperative pain levels, and a history of central nervous system disorders -- showed that patients with at least one copy of ApoE4 still had a significantly increased risk for early postoperative delirium (odds ratio 3.64, 95% confidence interval 1.51 to 8.77).
The authors recommended that further studies examine possible mechanisms whereby ApoE4 can lead to postoperative delirium, including how the allele may interact with other possible risk factors.
The authors noted that they could not determine the mechanism linking apolipoprotein genotype with delirium, and that by focusing on early-onset delirium they may have missed late-onset cases. Also, the sample size was not large enough to examine other allelic combinations, they noted, and they pointed out that it is still not known whether postoperative delirium in ApoE4 carriers is predictive of cognitive impairment.