Older adults with tooth loss have reduced brain volume in a region critical for memory compared with people who have most of their teeth. The finding adds to a growing body of evidence linking oral health to the development of Alzheimer鈥檚 disease.
Previous research has shown bacteria involved in gum disease can invade and damage brain regions affected by Alzheimer鈥檚. Gum disease is also a leading cause of tooth loss.
at the University of the Ryukyus in Japan and his colleagues examined tooth loss in more than 900 Japanese adults aged 60 years and older and scanned their brains using magnetic resonance imaging (MRI). Of the participants, 732 had no cognitive impairment while the rest either had dementia or mild cognitive impairment.
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After accounting for factors such as age, sex and education level, the researchers found no association between tooth loss and brain volume across all participants. However, when they focused only on those without cognitive impairment, they found some suggestive patterns. Those with fewer than 10 teeth had, on average, 3.5 per cent less volume in an area called the parahippocampal gyrus than those with more than 24 teeth. They also had an almost 25 per cent increase in lesions in the brain鈥檚 white matter, the bundles of nerve fibres connecting various brain regions.
These brain changes are seen in people with dementia, too. This is unsurprising given the parahippocampal gyrus plays a role in retrieving and encoding memories while white matter lesions contribute to cognitive decline.
鈥淭his could mean that people with less than 10 teeth are at risk of developing dementia,鈥� says Nakamura. As for why the researchers didn鈥檛 find similar associations between brain changes and tooth loss in the participants with dementia, it may be because other factors can contribute to the onset of the condition, he says. The lack of association might also be due to the small number of participants, says at King鈥檚 College London.
Whether tooth loss is a direct cause of these brain changes is unclear as the researchers only examined people at one time point. 鈥淚f they follow up with this cohort in a couple more years and see changes in white matter or other brain areas, we can have a better understanding about whether [tooth loss] is a significant factor in brain function,鈥� says Kang.
npj aging
