The Impact of Tooth Loss and Periodontitis on Hippocampal Atrophy: A Longitudinal Study in Late Middle-Aged and Older Adults

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Periodontitis is a chronic inflammatory disease that affects the gums and the bone that supports the teeth. It is caused by bacteria that accumulate in the dental plaque and trigger an immune response that damages the tissues. Periodontitis can lead to tooth loss, bad breath, and bleeding gums.

Although tooth loss and periodontitis have long been considered risk factors for Alzheimer’s disease, recent longitudinal research has challenged the notion of a significant association between these oral health conditions and hippocampal atrophy.

However, a new study aims to shed light on this topic by investigating the longitudinal association between the number of teeth present (NTP) and hippocampal atrophy, taking into account the severity of periodontitis, in a late middle-aged and older adult population.

The study focused on community-dwelling individuals aged 55 years and older who exhibited no cognitive decline. These participants underwent brain magnetic resonance imaging (MRI) and oral and systemic data collection at two separate time points, with a four-year interval between them.

The researchers utilized automated region-of-interest analysis to obtain hippocampal volumes from the MRI scans. To assess the severity of periodontitis, the mean periodontal probing depth (mean PD) was measured.

Multiple regression analysis was conducted, with the annual symmetric percentage change (SPC) of the hippocampal volume as the dependent variable. The researchers also included an interaction term between NTP and mean PD as the independent variable. To examine the interaction details, the Johnson-Neyman technique and simple slope analysis were employed.

Furthermore, a linear mixed-effects model was utilized to analyze the three-way interaction of NTP, mean PD, and time on hippocampal volume. The researchers also explored the interaction of NTP and time in subgroups divided by the median mean PD. To account for potential dropout bias, inverse probability weighting was applied in all models.

The analysis included data from 172 participants. The results revealed a significant qualitative interaction between NTP and mean PD concerning the annual SPC in the left hippocampus. Specifically, at the low-level mean PD (mean – 1 standard deviation), the regression coefficient of NTP on annual SPC in the left hippocampus was significantly positive.

This suggests that having fewer teeth was associated with a faster rate of left hippocampal atrophy in individuals with mild periodontitis. Conversely, at the high-level mean PD (mean + 1 standard deviation), the regression coefficient was significantly negative. This indicates that having more teeth was associated with a faster rate of hippocampal atrophy in individuals with severe periodontitis.

These findings were consistent with the results obtained from the linear mixed-effects model, where the interaction of NTP and time was significant in the higher mean PD group.

The findings of this study have important implications. In a late middle-aged and older cohort, the number of teeth present was found to have a differential effect on the rate of left hippocampal atrophy depending on the severity of periodontitis. These results suggest that maintaining good oral health, including a sufficient number of healthy teeth, may be crucial in mitigating the risk of hippocampal atrophy, especially in individuals with periodontal disease.

Further research is needed to explore the underlying mechanisms linking oral health to brain health and to investigate whether interventions targeting oral health can potentially contribute to the prevention or delay of Alzheimer’s disease.

In conclusion, this longitudinal study provides new insights into the association between tooth loss, periodontitis, and hippocampal atrophy. The findings indicate that the number of teeth present influences the rate of hippocampal atrophy in a context-dependent manner, depending on the severity of periodontitis. These results underscore the importance of maintaining good oral health and highlight the potential impact of oral health interventions on brain health in late middle-aged and older adults.



reference link: https://n.neurology.org/content/early/2023/07/05/WNL.0000000000207579

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