Does Weak Oral Function Increase the Risk of Lifestyle-Related Diseases?

Insights from the Latest Research on the Deep Connection Between Oral Health and Overall Health

Introduction: Your Teeth and Tongue May Be Sending “SOS” Signals

As we age, issues like weakened teeth, dry mouth, or difficulty moving the tongue gradually become more common. But what if these changes aren’t just signs of aging, but are actually linked to higher risks of lifestyle-related diseases such as high blood sugar, abnormal lipid levels, and reduced kidney function?

A recent study by researchers at Fujita Health University has revealed a clear connection between declining oral function and abnormal blood test results related to lifestyle diseases.

In this article, we’ll explain:

• How oral function is connected to lifestyle-related diseases
• Why checking your mouth can be the first step in managing overall health
• What practical actions you can take to maintain oral health

---

1. Why Oral Health and Overall Health Are Closely Linked

You may have heard that “periodontal disease can worsen diabetes.” Recent studies support this and have found that:

• Periodontal disease and diabetes negatively affect each other
• Poor oral health is linked to atherosclerosis and heart disease
• There is a strong relationship with chronic kidney disease (CKD)

Recent research also highlights that decreases in chewing ability, tongue movement, and saliva production can affect nutrition and overall health.

Key Points:
When oral function declines, it can:

• Limit the variety of foods you can eat
• Reduce stimulation to the brain and muscles from chewing
• Increase bacterial growth in the mouth

These factors can act as an “entry point” for various health problems.

---

2. Study Overview: Comparing Blood Tests and Oral Function in 118 Adults Aged 50+

The Fujita Health University research team analyzed data from 118 adults (over 50 years old) who underwent health checkups in 2021 and 2023.

Blood Tests (Related to Lifestyle Diseases)

• Fasting glucose (GLU)
• HbA1c (diabetes indicator)
• HDL cholesterol (good cholesterol)
• LDL cholesterol (bad cholesterol)
• BUN (kidney function)
• eGFR (kidney function)

Each value was classified as within or outside the normal range.

Oral Function Tests (7 Measures)

• Tongue Coating Index (TCI): Amount of white coating on the tongue
• Oral Dryness (ODN): Degree of tongue dryness
• Remaining Teeth Number (RTN)
• Oral Diadochokinesis (OD): Ability to repeat “Pa-Ta-Ka” quickly
• Tongue Pressure: Strength of the tongue
• Masticatory Function (MFN): Chewing ability
• Swallowing Function (EAT-10)

---

3. Study Results: Poor Blood Sugar, Lipid, or Kidney Function = Lower Oral Function

The results were striking: participants with higher risk indicators for lifestyle diseases consistently had lower oral function.

1) High Blood Sugar / HbA1c:

• Fewer teeth remaining
• Slower tongue movement (slower “Ta” and “Ka” sounds)

Damage to blood vessels from diabetes can worsen gum inflammation and reduce oral muscle function.

2) Abnormal Lipids (Low HDL / High LDL):

• Higher tongue coating index
• Lower oral diadochokinesis

Tongue coating can increase when tongue movement is weak or saliva production is reduced.

3) Poor Kidney Function (BUN / eGFR):

• Fewer teeth
• Higher tongue coating
• Slower tongue movement (“Ta” and “Ka”)

Chronic kidney disease has long been associated with poorer oral hygiene, and these findings support that.

---

4. Why Declining Oral Function May Affect Lifestyle Diseases

While causality cannot be confirmed, medical evidence suggests several mechanisms:

1) Reduced tongue and teeth function → Limited food variety

• Difficulty chewing meat, vegetables, seafood, or whole grains
• Leads to preference for carbohydrates or soft sweet foods → higher lifestyle disease risk

2) Tongue coating / periodontal disease → Systemic inflammation

• Bacteria and inflammatory molecules can enter the bloodstream
• Contributes to worsening diabetes, atherosclerosis, and kidney dysfunction

3) Dry mouth → Reduced saliva, more bacteria

• Saliva protects the body by washing away bacteria
• Less saliva = higher bacterial growth and inflammation

4) Declining oral function → Frailty

• Reduced food intake
• Loss of muscle mass
• Lower activity levels

---

5. Key Takeaway: Oral Health Is the Gateway to Overall Health

The study does not prove that “poor oral health directly causes disease,” but it clearly shows that people with lower oral function tend to have worse markers for lifestyle diseases.

Simple signs at home—number of teeth, tongue coating, dry mouth, tongue/lip movement—can reflect overall health.

---

6. How to Protect Your Oral Health

1) Brush teeth twice a day + clean your tongue

• Tongue coating is a bacterial hotspot
• Use a tongue brush gently from back to front once a day

2) Stimulate saliva glands if your mouth is dry

• Gently press the parotid, submandibular, and sublingual glands

3) Practice “Pa-Ta-Ka” exercises

• Repeat each sound for 5 seconds to strengthen tongue and lip muscles
• “Pa” = lips, “Ta” = tip of the tongue, “Ka” = back of the tongue

4) Get regular dental checkups

• Even if there’s no pain, checkups every 6–12 months help prevent oral and systemic disease

5) Chew food thoroughly

• More chewing → more saliva → lower blood sugar spikes → better satiety

---

7. Conclusion: Your Mouth Reflects Your Overall Health

Declining oral function = potential warning sign for lifestyle-related diseases.

Oral function declines are often subtle and may only be noticed when nutrition, muscle strength, or swallowing ability are already affected.

Protecting your oral health is a crucial step in disease prevention and extending healthy lifespan.

Quick Self-Check:

• Is your tongue coated white?
• Is your mouth often dry?
• Is it hard to pronounce “Ta” or “Ka”?
• Do you have trouble chewing hard foods?
• Haven’t visited the dentist in over six months?

Even one of these signs may be your body sending a small “SOS.” Oral care is the first step to protecting your body’s future health—start today!

References

Kanie H, Yoshida M, Yokoi M, Okamoto M, Sasaki H, Ono K. Relationship Between Blood Test Results and Oral Function Tests in Individuals Undergoing Regular Physical Examinations. J Oral Rehabil. 2025 Sep;52(9):1261–1266. doi: 10.1111/joor.13977. Epub 2025 Apr 17. PMID: 40247468.