Abstract
BACKGROUND: The presence of the apolipoprotein E4 (APOE4) allele and periodontal disease are independently correlated with higher levels of amyloid-β and inflammation in the brain, worse cognition, and Alzheimer's disease. OBJECTIVE: To assess whether the presence of the APOE4 allele modifies the relationship between IgG antibodies against periodontal microorganisms and cognitive function in older adults participating in the NHANES III study. METHODS: This cross-sectional analysis was conducted among participants of the third National Health and Nutrition Examination Survey (NHANES III) (1988 to 1994), aged 60 years and older, with measurements of IgG antibodies against 19 periodontal microorganisms and APOE4 alleles (N = 1644). RESULTS: Approximately 77.5% of participants carried no APOE4 allele, 20.0% had one allele, and 2.6% were homozygous. Mean cognitive scores were 16.1, 16.0, and 15.3 for non-carriers, heterozygous, and homozygous APOE4 allele carriers, respectively (p = 0.01). Antibody groups were not correlated with APOE4 carrier status. The Orange-Blue cluster (antibodies against E. nodatum, A. naeslundii) was correlated with cognitive score (Spearman r = 0.08, p < 0.001), but not other antibody groups. In the multivariable-adjusted models, APOE4 alleles did not modify the associations between antibody clusters and cognitive score (p-interaction > 0.05). CONCLUSIONS: Mean cognitive scores were lower among APOE4 carriers. The APOE4 allele did not modify associations between groups of IgG antibodies against periodontal microorganisms and cognition among older aged adults without cognitive impairment. These findings need to be verified in larger prospective studies.