Periodontal disease and the oral-systemic connection: "is it all the RAGE?"

Associations Between Oral Health Status, Perceived Stress, and Neuropsychiatric Symptoms Among Community Individuals With Alzheimer's Disease: A Mediation Analysis

Community individuals with Alzheimer's disease (AD) experience oral disease alongside neuropsychiatric symptoms (NPS) with disease progression. Despite growing evidence for the link between oral health and cognitive status, few studies have investigated the associations between oral health and NPS, especially based on individuals' experience of AD. The primary aim of this study was to examine (a) the difference in oral health-related stressors among individuals with AD, mild cognitive impairment (MCI), and subjective cognitive decline (SCD); and (b) the associations of these stressors with NPS under the framework of the stress process model (SPM). A cross-sectional study was conducted among individuals diagnosed with AD (n = 35), MCI (n = 36) or SCD (n = 35), matched for age, sex education, and body mass index (BMI). Multiple regression and mediation model analyses were performed to explore predictors and their relationships with NPS based on the SPM. Data collection comprised four sections: (a) individual context; (b) oral health-related stressors, including dental caries, periodontal status, oral hygiene, the geriatric oral health assessment index (GOHAI), oral salivary microbiota, pro-inflammatory cytokines, and oral health behavior; (c) subjective stressors (i.e., perceived stress [PS]); and (d) NPS. Decayed, missing, and filled teeth (DMFT), missing teeth (MT), loss of attachment (LoA), plaque index (PLI), PS, oral health behavior, GOHAI, pro-inflammatory cytokines, and salivary bacterial composition were significantly different among the three groups; these parameters were poorer in the AD group than SCD and/or MCI group. LoA, PLI, PS, and pain or discomfort in the GOHAI were directly associated with NPS. PLI, LoA, and psychosocial function in the GOHAI indirectly affected NPS, and this relationship was mediated by PS. Individuals with AD reported greater oral health-related stressors. This study identifies direct and indirect associations linking oral health-related stressors and PS with NPS in individuals with AD. Our findings suggest that targeted dental care and oral-related stressor control may be valuable for managing NPS.

Porphyromonas gingivalis and digestive system cancers

Porphyromonas gingivalis (P. gingivalis) is an anaerobic gram-negative bacterium that colonizes in the epithelium and has been strongly associated with periodontal disease. Recently, various degrees of associations between P. gingivalis and digestive system cancers, including oral squamous cell carcinoma in the oral cavity, oesophageal squamous carcinoma in the digestive tract, and pancreatic cancer in pancreatic tissues, have been displayed in multiple clinical and experimental studies. Since P. gingivalis has a strong association with periodontal diseases, not only the relationships between P. gingivalis and digestive system tumours but also the effects induced by periodontal diseases on cancers are well-illustrated in this review. In addition, the prevention and possible treatments for these digestive system tumours induced by P. gingivalis infection are also included in this review. At the end, we also highlighted the possible mechanisms of cancers caused by P. gingivalis. One important carcinogenic effect of P. gingivalis is inhibiting the apoptosis of epithelial cells, which also plays an intrinsic role in protecting cancerous cells. Some signalling pathways activated by P. gingivalis are involved in cell apoptosis, tumourigenesis, immune evasion and cell invasion of tumour cells. In addition, metabolism of potentially carcinogenic substances caused by P. gingivalis is also one of the connections between this bacterium and cancers.