There is a well described association between systemic infection such as urinary tract and pneumonia (and periodontitis) with exacerbations of cognitive decline in AD associated with changes in the host's inflammatory response to the presence of systemic pathogens.22 Furthermore, the presence of APOE ε4 has been implicated in an aggressive form of periodontitis in a Chinese population.23 In accord with finding P. gingivalis in the brain tissue of patients who died of confirmed AD.24,25. This evidence concerns the gene APOE and periodontitis.