July 8 (UPI) -- Older adults who experience tooth loss are at increased risk for cognitive impairment and dementia, and their risk grows with each tooth lost, a study published Thursday by JAMDA: The Journal of Post-Acute and Long-Term Care Medicine found.
However, older adults with dentures do not share this increased risk, suggesting that timely treatment with implants may protect against cognitive decline, the researchers said.
"Our findings underscore the importance of maintaining good oral health and its role in helping to preserve cognitive function," study co-author Bei Wu said in a press release.
"It's important to gain a deeper understanding of the connection between poor oral health and cognitive decline," said Wu, a professor of global health at New York University in New York City.
Dementia affects up to 6 million people in the United States, but as many as 11% of adults nationally experience some degree of cognitive decline, the Alzheimer's Association estimates.
About one in six adults age 65 and older experiences significant tooth loss as they age, according to the Centers for Disease Control and Prevention.
Missing teeth can lead to problems chewing, which may contribute to nutritional deficiencies or promote potentially harmful brain chemistry changes, Wu and her colleagues said.
A connection also may exist between gum disease, a leading cause of tooth loss, and cognitive decline, the researchers said.
In addition, tooth loss may reflect life-long socioeconomic disadvantages that also increase a person's risk for cognitive decline, including reduced access to quality healthcare.
For this analysis, Wu and her colleagues compiled data from 14 studies of tooth loss and cognitive impairment that involved 34,074 adults, 4,689 of whom had diminished cognitive function.
Adults with more tooth loss had a nearly 50% higher risk for developing cognitive impairment and a nearly 30% higher risk for being diagnosed with dementia, compared with those who did not lose their teeth.
However, adults missing teeth were 48% more likely to have cognitive impairment if they did not have dentures compared with those with dentures, the researchers said.
A greater number of missing teeth was also linked with a higher risk for cognitive decline, with each additional missing tooth associated with a 1.4% increased risk for cognitive impairment and 1.1% increased risk for a dementia diagnosis.
"[There is a] 'dose-response' relationship between the number of missing teeth and risk of diminished cognitive function," study co-author Xiang Qi said in a press release.
"[This] substantially strengthens the evidence linking tooth loss to cognitive impairment, and provides some evidence that tooth loss may predict cognitive decline," said Qi, a doctoral candidate at New York University.