Association between clusters of antibodies against periodontal microorganisms and Alzheimer disease mortality: Evidence from a nationally representative survey in the USA

Abstract Background Alzheimer disease (AD) has been linked with periodontal microorganisms such as Porphyromonas gingivalis in observational and mechanistic studies. IgG antibodies against periodontal microorganisms which are markers of past and current periodontal infection have been correlated with cognitive impairment. We examined associations between empirically derived groups of 19 IgG antibodies against periodontal microorganisms and AD mortality. Methods Individuals participating in the Third National Health and Nutrition Examination Survey (NHANES III) with complete data on IgG titers were followed up between 1988 and December 31, 2019. The outcome was AD mortality, and the main exposures were IgG antibodies against periodontal microorganisms classified into four mutually exclusive groups using cluster analysis. Survey‐weighted Cox proportional hazard models were used to evaluate adjusted hazard ratios (aHR) and 95% confidence intervals (CI) for the relationship between clusters and AD mortality. Results With up to 21 years of follow‐up, 160 AD‐related deaths were documented. In the multivariable‐adjusted model, AD mortality overall was not associated with the Red‐Green (aHR 1.18; 95% CI, 0.46–3.07), Yellow‐Orange (aHR 1.36; 95% CI, 0.58–3.19), Orange‐Blue (aHR 0.63; 95%, CI, 0.33–1.21), and the Orange‐Red (aHR 0.79; 95% CI, 0.37–1.70) when the upper tertiles were compared to the bottom tertiles. However, the subgroup of middle‐aged individuals in the highest tertile of the Red‐Green cluster, but not older individuals, had a 13% higher risk of AD mortality (aHR 1.13; 95% CI, 1.02–1.26) compared with those in the bottom tertile. Conclusion Clusters of IgG antibodies against periodontal microorganisms did not predict AD mortality in this study.