Abstract: Periodontitis has become one of the most widespread chronic inflammatory diseases worldwide, affecting roughly 11% of the adult population. In China, periodontal health is notably poor, with less than 10% of individuals over the age of 35 maintaining periodontal health, while the prevalence of periodontitis in middle-aged and elderly populations reaches as high as 82.6%. From a public health perspective, periodontitis not only seriously compromises oral health but is also closely linked to multiple chronic systemic diseases, including cardiovascular disease, diabetes mellitus, and cognitive impairment. A substantial body of cohort studies and meta-analyses consistently demonstrate that patients with periodontitis are at a significantly increased risk of cardiovascular events. Moreover, periodontitis tends to progress more rapidly in individuals with diabetes, highlighting a bidirectional causal relationship between these two conditions. Our research team has maintained a long-term focus on elucidating the relationship between periodontitis and systemic diseases within Chinese community populations. In this review, we comprehensively summarize epidemiological findings on the associations between periodontitis and cardiovascular disease, metabolic syndrome, and cognitive decline, specifically drawing on data from Chinese cohorts. Complementing these observations, animal experiments provide evidence that experimental periodontitis can induce glucose intolerance and accelerate the development of atherosclerotic lesions. At the mechanistic level, we preliminarily validate that mitochondrial DNA efflux and the hematogenous spread of periodontal pathogens may act as biological conduits bridging local periodontal inflammation with systemic pathologies. We also address current challenges in the field, including difficulties in disentangling causal relationships due to confounding comorbidities like diabetes and cardiovascular diseases, which often coexist and influence each other. To advance understanding, there is an urgent need for well-designed longitudinal and interventional studies employing advanced causal inference methods. Ultimately, this work aims to deepen the current knowledge of periodontitis ' systemic effects and to support the development of evidence-based public health strategies for integrating oral health into chronic disease prevention efforts in China.

Key words: Periodontitis, Systemic diseases, Cardiovascular disease, Diabetes mellitus, Cognitive impairment, Mitochondrial DNA, Pathogen dissemination