# Oral Health and Cognitive Decline: A Systematic Review of the Periodontitis-Alzheimer's Connection
## 3 Results
\begin{table}
\begin{tabular}{c c c c c} \hline
**Authors** & **Type of Study** & **Aim of Study** & **Matherials and Methods** & **Results** \\ \hline \multirow{9}{*}{[PERSON] et al. (2017)[222]} & & \multicolumn{2}{c}{Retrospective} \\  & & Investigate whether & matched-cohort study using & 10 years of CP exposure was \\  & & chronic periodontitis & National Health Insurance & associated with 1.707-fold \\  & & (CP) increases the risk & Research Database (NHIRD) & increase in AD risk. Study \\  & & cohort study & of developing & \\  & & Alzheimer’s & 9291 CP patients and & highlighted role of chronic \\  & & & disease (AD). & 18,672 matched non-CP & inflammation as potential \\  & & & controls, followed over & pathway linking CP to AD. \\  & & & 16 years. & \\ \hline \multirow{9}{*}{[PERSON] et al. (2024)[223]} & \multicolumn{2}{c}{Characterize} \\  & & subgingival & & \\  & & microbiomes and & cross-sectional study, 16S & Identified 165 metabolites \\  & & gingival circular & rRNA sequencing, & and 16 species associated \\  & & metabolic signatures in & LC-MS/MS. & with cognitive function. \\  & & AD and aMCI patients. & & \\ \hline \multirow{9}{*}{[PERSON] et al. (2024)[224]} & \multirow{9}{*}{Cross-sectional MRI} & \multicolumn{2}{c}{Examine the association of} & Study with 486 participants, clinical periodontal data, microbial and serum samples, brain MRIs & Higher tooth retention linked \\  & & study & with MRI markers of & samples, brain MRIs & to favorable MRI outcomes; \\  & & Alzheimer’s disease & analyzed using & severe periodontitis \\  & & and cognitive aging. & regression models. & associated with \\ \hline \multirow{9}{*}{[PERSON] et al. (2024)[225]} & \multirow{9}{*}{Longitudinal cohort} & \multicolumn{2}{c}{Examine the interplay of infection burden and periodontal pathogens} & NHANES III (1988–1994) & Hepatitis C and herpes \\  & & & periodontal pathogens & survey data linked to \\  & & study & with incident & \\  & & & with incident & \\  & & Alzheimer’s and & 2975 participants, Cox & risk. Periodontal pathogens \\  & & & all-cause dementia. & proportional hazards model. & minority groups. \\ \hline \multirow{9}{*}{[PERSON] et al. (2022)[226]} & \multirow{9}{*}{Quasi-experimental} & \multicolumn{2}{c}{Quasi-experimental design} & Quasi-experimental design: 177 periodontally treated patients (GANL MED cohort) & Periodontal treatment had \\  & & & compared to 409 untreated & favorable effect on \\  & & & subjects (SHIP-TREND & AD-related brain atrophy \\  & & periodontal treatment & cohort). Brain atrophy & (mean shift \(-\)0.41; 95\% CI \\  & & and preclinical & markers and MRI outcomes & \(-\)0.70— 0.12; \(p\) = 0.0051). \\  & & Alzheimer’s & analyzed over median & Brain aging effects were \\  & & & observation period of & uncertain. Strong evidence of \\  & & & 7.3 years. Propensity score & link between periodontitis \\  & & & matching and sensitivity & and preclinical AD. \\  & & & analyses were used to adjust & \\  & & & for confounders. & \\ \hline \multirow{9}{*}{[PERSON] et al. (2021)[227]} & \multirow{9}{*}{Case–control study with systemic markers} & \multicolumn{2}{c}{Pig abundance was} \\  & & & significantly higher in ND \\  & & & patients compared to no-ND \\  & & & and HC (\(p\) \(<\) 0.01). & \\  & & & 28 with no-ND) and & Correlation between Pg \\  & & & abundance and anti-Pig \\  & & & antibody levels was \\  & & & observed in no-ND but not \\  & & & in ND, suggesting impaired \\  & & & immune response in ND. No \\  & & & link was found with systemic \\  & & & inflammation markers. \\  & & & Study supports bidirectional \\  & & & oral-brain connection. \\ \hline \end{tabular}
\end{table} 
Table 2: _Cont._