Epidemiologic studies of the association between periodontal disease and cardiovascular disease, including stroke, had mixed findings.1 Some studies have found that serum antibodies to major periodontal pathogens are associated with coronary heart disease (CHD), suggesting that periodontal infection or the host response to periodontal infection may play a causal role in CHD.1 More recently, longitudinal studies have supported an association of periodontal disease between cognitive decline and dementia.2 The motivation for these studies has been two-fold. First, periodontal disease is known to be associated with systemic inflammation,3 which, in turn, is known to be causally associated with atherosclerotic disease.4 Second, periodontal disease is potentially modifiable in the population. The limitation of all observational epidemiologic studies is the problem of confounding by incompletely measured or unmeasured variables, such as diet, health behaviors including oral hygiene, and the host response to infection. In addition, studies oral health and either cognitive decline or dementia may suffer from reverse causality; cognitive changes may lead to lessened oral hygiene and periodontal disease.