Look after your teeth to protect against cognitive decline in old age © Getty Images

Look after your teeth to protect against cognitive decline in old age

With each lost tooth, the risk of cognitive impairment grows – but not for those who have dentures.

Tooth loss is linked to cognitive decline and dementia, a study at NYU Rory Meyers College of Nursing has found. However, the researchers did not see the same effect in older adults with dentures.

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The team analysed 14 studies on the link between tooth loss and cognitive function, involving a total of over 34,000 adults. They found that tooth loss was linked to a 1.48 times higher risk of cognitive decline, and a 1.28 times higher risk of dementia, even after they controlled for other factors.

However, those who had dentures did not have the same risk. In fact, the researchers found no significant link between tooth loss and cognitive decline in people with dentures. People with missing teeth were more likely to be cognitively impaired if they didn’t have dentures.

“Given the staggering number of people diagnosed with Alzheimer’s disease and dementia each year, and the opportunity to improve oral health across the lifespan, it’s important to gain a deeper understanding of the connection between poor oral health and cognitive decline,” said Bei Wu, Dean’s Professor in Global Health at NYU Rory Meyers College of Nursing.

Previous research has shown a link between oral health and cognitive impairment and dementia, though it’s not clear what causes it. Some researchers have suggested that missing teeth could cause difficulty chewing, which could lead to nutritional deficiencies in the brain. Other studies have pointed to a link between gum disease and Alzheimer’s disease. Alternatively, it could be that tooth loss is a symptom of socioeconomic deprivation, which is also a risk factor for cognitive decline.

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The researchers also found that each lost tooth raised the risk of cognitive impairment by 1.4 per cent and dementia by 1.1 per cent. They call this a ‘dose-response’ association – that is, the greater the cause (tooth loss), the greater the effect (cognitive decline).

“This ‘dose-response’ relationship between the number of missing teeth and risk of diminished cognitive function substantially strengthens the evidence linking tooth loss to cognitive impairment, and provides some evidence that tooth loss may predict cognitive decline,” said Xiang Qi, a doctoral candidate from NYU Meyers.

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The researchers suggest that good oral hygiene may even be protective. “Our findings underscore the importance of maintaining good oral health and its role in helping to preserve cognitive function,” said Wu.

Reader Q&A: Does flossing your teeth really make a difference?

Asked by: Ian Styles, London

For years, dentists have told us to floss as well as brush our teeth. And it seems to make sense: less gunk between our teeth should lead to less decay. Yet surprisingly, there’s little evidence it’s true, as it’s never been put to the test in a large clinical trial.

Some small studies have found that flossing helps combat gum disease, but there’s no compelling evidence that it also stops tooth decay. So does that mean it’s pointless? Not at all. First, gum disease is a major cause of tooth loss. And second, just because researchers haven’t done a proper study, it doesn’t mean flossing can’t also prevent tooth decay: the absence of evidence doesn’t mean there’s no effect.

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