Cerebrovascular risk factors and preclinical memory decline in healthy APOE ε4 homozygotes

Objective: To characterize the effects of cerebrovascular (CV) risk factors on preclinical memory decline in cognitively normal individuals at 3 levels of genetic risk for Alzheimer disease (AD) based on APOE genotype. Methods: We performed longitudinal neuropsychological testing on an APOE epsilon 4 enriched cohort, ages 21-97. The long-term memory (LTM) score of the Auditory Verbal Learning Test (AVLT) was the primary outcome measure. Any of 4 CV risk factors (CVany), including hypercholesterolemia (CHOL), prior cigarette use (CIG), diabetes mellitus (DM), and hypertension (HTN), was treated as a dichotomized variable. We estimated the longitudinal effect of age using statistical models that simultaneously modeled the cross-sectional and longitudinal effects of age on AVLT LTM by APOE genotype, CVany, and the interaction between the two. Results: A total of 74 APOE epsilon 4 homozygotes (HMZ), 239 epsilon 4 heterozygotes (HTZ), and 494 epsilon 4 noncarriers were included. APOE epsilon 4 carrier status showed a significant quadratic effect with age-related LTM decline in all models as previously reported. CVany was associated with further longitudinal AVLT LTM decline in APOE epsilon 4 carriers (p = 0.02), but had no effect in noncarriers. When epsilon 4 HTZ and HMZ were considered separately, there was a striking effect in HMZ (p < 0.001) but not in HTZ. In exploratory analyses, significant deleterious effects were found for CIG (p = 0.001), DM(p = 0.03), and HTN (p = 0.05) in APOE epsilon 4 carriers only that remained significant only for CIG after correction for multiple comparisons. Conclusion: CV risk factors influence age-related memory decline in APOE epsilon 4 HMZ. Neurology (R) 2011;76:1078-1084