Apolipoprotein E ε4 and cognitive function after surgery in middle-aged and elderly Danish twins.

BACKGROUND Transient cognitive impairment is common in adult patients of all ages following anaesthesia and surgery. Apolipoprotein E (APOE) e4 carriers may have a larger deterioration in short-term cognitive function after major surgery compared with APOE e4 noncarriers. OBJECTIVES The aim was to examine the effect of APOE e4 on the association between exposure to surgery and anaesthesia, and subsequent cognitive functioning. A more pronounced deterioration in cognitive function in APOE e4 carriers was hypothesised. DESIGN An observational cross-sectional and a 6 to 10 years longitudinal twin cohort design. SETTING Survey and register study of 2936 Danish twins aged 45 to 92 years. MAIN OUTCOME MEASURES Cognitive function was assessed using five age-sensitive cognitive tests. In the cross-sectional study, we compared twins exposed to surgery with a reference group (unexposed). Linear regression models were used adjusting for sex and age and stratified by APOE e4 carrier status. In the longitudinal cognitive follow-up study 1671 twins participated. Intrapair analyses were also performed using 70 same-sexed twin pairs concordant for APOE e4 carrier status, but discordant for major surgery. RESULTS APOE e4 carriers had lower cognitive scores compared with noncarriers, and this was statistically significant in elderly twins 70+ years of age (mean difference, -0.67; 95% CI, -1.14 to -0.17). There was no significant impact on cognitive function after surgery according to APOE e4 carrier status in the cross-sectional study. Similarly, there was no APOE e4 modification in the longitudinal study. Also, in the intrapair analyses no evidence was found of lower cognitive score after major surgery compared with the nonexposed cotwins among APOE e4 carriers. CONCLUSION No evidence was found of more pronounced long-term deterioration in cognitive function after surgery among APOE e4 carriers, but elderly APOE e4 carriers in general performed worse on the cognitive tests than noncarriers.