Association between APOE epsilon 4 allele and postoperative cognitive dysfunction: A meta-analysis

Background: Carriers of the apolipoprotein E epsilon 4 allele (APOE epsilon 4) may be at increased risk of postoperative cognitive dysfunction (POCD), but this association has not been reported consistently. We conducted a meta-analysis to derive a more precise conclusion. Methods: The PubMed, EBSCO and EMBASE databases were searched for eligible studies published in English before March 2013. The association between APOE epsilon 4 and POCD was expressed by the odds ratio (OR) with 95% confidence interval (CI). Funnel plots were constructed and publication bias assessed by Egger's test. Results: Nine studies encompassing 1063 APOE epsilon 4 carriers and 2983 noncarriers were included. At about 1-week postsurgery, a significant association between APOE epsilon 4 and POCD was found (OR 1.83, 95% CI: 1.18-2.85), but the association was no longer significant after removing one large study (OR 1.35, 95% CI: 0.92-1.97). Stratified analysis of cardiac/vascular surgery patients also yielded no significant correlation (OR 1.62, 95% CI: 0.80-3.28). One to three months postsurgery, neither the overall analysis (OR 1.56, 95% CI: 0.87-2.81) nor the stratified analysis of cardiac/vascular surgery patients (OR 3.33, 95% CI: 0.55-20.22) indicated a significant correlation. APOE epsilon 4 was also not correlated with POCD at 1-year postsurgery (OR 1.15, 95% CI: 0.71-1.86). No evidence of publication bias was revealed by Egger's test. Conclusions: The APOE epsilon 4 allele was associated with a significantly increased POCD risk about 1-week postsurgery, but the association depended on one large study. No association was found 1-3 months and 1-year postsurgery.