By Danielle 
A new Japanese study has found that older adults with abnormal blood test results may also have declining oral health—suggesting a potential link between oral function and the risk of lifestyle-related diseases.
The study, published online in the Journal of Oral Rehabilitation on April 17, 2025, was led by Professor Mitsuyoshi Yoshida, chair of the Department of Dentistry and Oral-Maxillofacial Surgery at Fujita Health University’s School of Medicine. It examined 118 people aged 50 and older who had undergone routine medical check-ups.
“Our main aim was to investigate the link between oral health and blood test results for glucose metabolism, lipid levels and kidney function,” said Yoshida.
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Seven oral function tests
Researchers collected data from dental exams conducted in 2021, along with annual physical examinations from both 2021 and 2023. Participants completed seven different oral function tests to provide a comprehensive view of their oral health. These included:
- Tongue coating index (TCI), a marker of oral hygiene
- Oral dryness
- Number of remaining functional teeth
- Maximum tongue pressure
- Masticatory (chewing) function
- Swallowing function
- Oral diadochokinesis (OD)—a test measuring how quickly and accurately participants could repeat specific syllables
Participants were then divided into two groups based on whether their blood test results—including fasting blood glucose, cholesterol and kidney function—fell within standard reference ranges.
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Key findings included:
- Blood sugar: Participants with fasting blood glucose and HbA1c levels outside the reference range had significantly fewer remaining teeth and lower OD scores compared to those within the range.
- Cholesterol: Those with elevated cholesterol also showed higher TCI values and lower OD scores, suggesting poorer oral hygiene and oral motor function.
- Kidney function: Participants with abnormal estimated glomerular filtration rate (eGFR) values, a measure of kidney function, also had significant differences in several oral function tests.
What researchers recommend
The study adds to growing evidence that poor oral health may increase the risk of developing conditions such as diabetes, heart disease and kidney dysfunction. The researchers recommend incorporating oral function testing into routine health check-ups to support better overall health outcomes.