Association between APOE ε4 allele and vascular dementia: The cache county study

Background: The APOE ε4 allele is an established risk factor for Alzheimer's disease, but reports of its association with vascular dementia (VaD) have been inconsistent. We examined the relationship between APOE ε4 allele and the risk of incident VaD in a large, population-based cohort of elderly adults with up to 10 years of follow-up between 1995 and 2005. Methods: A total of 3,424 elderly men and women free of dementia were genotyped at the baseline assessment. Incident VaD was identified through standardized procedures administered at 3 follow-up assessments. Cox proportional hazards models were used to evaluate the risk of VaD associated with APOE ε4. Results: The adjusted hazard ratio was 1.6 for the participants with 1 APOE ε4 allele (95% CI: 0.9-2.7; p = 0.083) and 4.4 for those with 2 APOE ε4 alleles (95% CI: 1.6-12.5; p = 0.005). The increased risk did not appear to be mediated by vascular risk factors. Conclusions: The APOE ε4 allele is associated with an increased risk of VaD in a dose-dependent fashion and accounts for almost 20% of VaD in the population.