Everyone dreads losing their teeth as they age, and undergoing costly and painful treatment. There may, however, be a bigger concern, as scientists have now linked tooth loss to dementia.
Dementia is an umbrella term for a loss of brain function, with Alzheimer's being the most common form of the disease.
Many forms of dementia are brought on by an abnormal build-up of proteins in the brain, causing nerve cells to die and areas of the vital organ to shrink. Why this occurs, however, is often unclear.
Tooth loss has previously been linked to cognitive decline – defined as memory loss, difficulty concentrating and impaired reasoning that does not "cause problems" in a person's day-to-day life.
To better understand how oral health relates to dementia, scientists from New York University analysed 14 studies with more than 34,000 participants between them.
Results – published in JAMDA: The Journal of Post-Acute and Long-Term Care Medicine – reveal those who had lost teeth were 1.48 and 1.28 times more likely to develop cognitive impairment and dementia, respectively.
Missing teeth may lead to difficulty chewing, which could cause nutritional deficiencies that affect the brain. Gum disease, a leading cause of tooth loss, is also increasingly being linked to cognitive decline.
Around 850,000 people in the UK have dementia, which is expected to rise to 1.6 million by 2040.
UK data are muddled, however, one in six adults aged 65 or over in the US have lost all of their teeth.
"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 study author Dr Bei Wu.
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Of the 34,000 study participants, more than 4,000 had "diminished cognitive function".
The New York scientists found tooth loss was linked to dementia and cognitive decline, after adjusting for other risk factors that raise the risk of memory loss.
Tooth loss may reflect a life-long social disadvantage, another risk factor for dementia, according to the scientists.
Every additional missing tooth was associated with a 1.4% and 1.1% increased risk of cognitive impairment and dementia, respectively.
"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 co-author Xiang Qi.
Dementia was not linked to having dentures, suggesting timely treatment may ward off cognitive decline.
"Our findings underscore the importance of maintaining good oral health and its role in helping to preserve cognitive function," added Qi.
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