Medical advances and better knowledge of health have contributed to increased life expectancy and a growing elderly population; with that, there has also been an increase in age-related chronic conditions such as dementia. Dementia contributes significantly to the disease burden globally and results in the deterioration of brain functioning, affecting memory, speech, and thinking abilities. Leading data and analytics company GlobalData‘s epidemiologists estimate that by the end of 2024, there will be 3.5 million diagnosed prevalent cases of men and women 60 years and older who have dementia in Japan. That number is predicted to increase to 4.0 million by the end of 2032.
There has been a longstanding association between poor oral hygiene and cognitive decline, including the risk of developing dementia. Other studies have theorised that poor occlusal contact (inadequate contact between teeth) has negative impacts on brain functions due to diminished sensory input and nutritional deficits. Miyano and colleagues tested this popular hypothesis further by quantifying whether poor masticatory function due to poor posterior occlusal contact is associated with an increased risk of dementia, in a longitudinal observational study, published in Nature in November 2024. Proper occlusal contact, in particular in the posterior region, plays an important role in mastication and dental function and thus relates to the overall immune function.
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In this study, men and women under the age of 75 years were enrolled. Data on 931,309 individuals was obtained from the JMDC Tokyo, Japan, Claims Database; patients who were enrolled in the study were initially free of dementia, and over the period of 2016 to 2022, patients underwent medical check-ups and were classified into one of three groups based on the Eichner classification, groups A, B, and C. In an average follow-up period of 35.6 months, 691 incident cases of dementia were identified by the ICD-10 code. A significant difference in the time to event, dementia, was detected between the three groups. The proportion of dementia cases was significantly higher in the Eichner B and C groups, with reduced or absent posterior occlusal contact than in group A, which had adequate occlusal contact. The findings from this study corroborate findings from previous studies on poor masticatory function and cognitive decline. From a public health perspective, these newly found results by Miyano on poor occlusal contact could help reinforce checking for the location of missing teeth at dental check-ups to identify those at risk of dementia. It also warrants further research into whether prosthetics could be a good resolution for decreasing dementia risk in those who have poor occlusal contact.
One aspect of this study to be cautious of is that the sample was composed of those under the age of 75 years, so the generalisability of these study findings to the 75-years-and-older population may be limited.
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