Key Takeaways
- A new cross-sectional analysis of 17,833 NHANES participants older than 40 linked greater tooth loss with poorer kidney function, but the clearest adjusted association appeared among women.
- Women in the highest tooth-loss quartile had 37.9% higher adjusted odds of having an estimated glomerular filtration rate below 60 mL/min/1.73 m² than women in the lowest quartile.
- The study does not prove that losing teeth damages the kidneys, that kidney disease causes tooth loss, or that replacing missing teeth will improve kidney function.
- Tooth loss can reflect periodontitis, tooth decay, smoking, diabetes, aging, limited access to dental care, and other factors that also relate to kidney health.
- Statistical analyses suggested possible indirect roles for oxidative balance and systemic inflammation, but the cross-sectional design cannot establish either factor as a biological mediator.
- The researchers did not apply NHANES survey weights or account for its complex sampling design, so the findings describe the analyzed sample rather than the entire U.S. population.
- Extensive tooth loss is not a diagnostic test for chronic kidney disease, but it may prompt a broader health conversation when a patient also has diabetes, hypertension, older age, or other kidney risk factors.
Introduction
New research found an association between greater tooth loss and poorer kidney function, particularly among women, but it does not establish causation.
Teeth do not disappear for one reason, and kidney function does not decline through one pathway. Yet both problems often accumulate alongside aging, diabetes, smoking, inflammation, socioeconomic disadvantage, and limited access to preventive care. That overlap makes oral-systemic research important, but it also makes the findings easy to overstate.
A new study published in The Saudi Dental Journal analyzed data from 17,833 participants in the U.S. National Health and Nutrition Examination Survey, or NHANES. The researchers found that greater tooth loss correlated with lower estimated kidney function. After adjustment for multiple demographic and health factors, the strongest categorical association remained among women (Gong et al., 2026).
The finding deserves attention, but the most responsible interpretation is not that missing teeth damage the kidneys. The study measured tooth status, laboratory values, diet, lifestyle, and other variables at the same general point in time. It could identify patterns, but it could not determine which condition came first or whether one caused the other.
From a dental perspective, the study supports a broader view of tooth loss. Missing teeth may serve as a visible record of accumulated oral and systemic vulnerability. They do not provide a kidney diagnosis, but in the right clinical context, they may justify asking additional questions about a patient’s overall health.
What Did the Researchers Study?
Gong and colleagues pooled NHANES data collected from 2001 through 2020. They began with 97,657 participants and excluded people aged 40 or younger as well as those who lacked the necessary dental, kidney, lifestyle, inflammatory, or covariate data. The final sample included 8,824 men and 9,009 women (Gong et al., 2026).
The researchers counted missing permanent teeth from a possible total of 28, excluding wisdom teeth. They classified a position as missing only when it contained neither a natural tooth nor a dental restoration.
To estimate kidney function, the investigators calculated the estimated glomerular filtration rate, or eGFR, from serum creatinine with the 2021 CKD-EPI equation. They classified participants with an eGFR below 60 mL/min/1.73 m² as having eGFR-defined chronic kidney disease. In the analytic sample, 1,837 participants met that definition, while 15,996 did not (Gong et al., 2026).
The analysis adjusted for age, race and ethnicity, education, income relative to poverty, smoking, alcohol consumption, body mass index, hypertension, and diabetes. These adjustments matter because many of the same factors influence both oral health and kidney health.
The researchers also explored two possible indirect statistical pathways:
- The oxidative balance score, or OBS, combined 16 dietary components and four lifestyle factors into a measure of pro-oxidant and antioxidant exposure.
- The systemic immune-inflammation index, or SII, combined platelet, neutrophil, and lymphocyte counts into a marker of systemic immune-inflammatory status.
These measures allowed the investigators to ask whether oxidative balance and systemic inflammation might statistically account for part of the association between tooth loss and eGFR. They did not allow the investigators to establish a biological chain of cause and effect.
What Did the Study Find?
Across the complete sample, each additional missing tooth correlated with a small reduction in eGFR after adjustment. However, the adjusted relationship between tooth-loss quartiles and the odds of eGFR-defined CKD did not remain statistically significant for the overall sample (Gong et al., 2026).
The female-specific results were more consistent. Among women, each additional missing tooth corresponded to an adjusted eGFR reduction of 0.074 mL/min/1.73 m². Women in the highest tooth-loss quartile had an eGFR that averaged 1.291 mL/min/1.73 m² lower than women in the lowest quartile. They also had 1.379 times the adjusted odds of eGFR-defined CKD, which represents 37.9% higher odds, not a 37.9% greater probability of disease (Gong et al., 2026).
Among men, the continuous model also showed a small decrease in eGFR with each additional missing tooth. However, the categorical comparisons did not reveal a clear adjusted difference between the higher and lowest tooth-loss quartiles, and the adjusted association with eGFR-defined CKD did not remain significant.
This distinction matters. A headline stating that tooth loss predicts kidney disease in all adults would go beyond the results. The main adjusted CKD association appeared among women in this particular analytic sample.
How Large Was the Difference?
Statistical significance does not automatically mean a large clinical effect. The adjusted eGFR difference between women in the highest and lowest tooth-loss quartiles was about 1.3 mL/min/1.73 m². Clinicians interpret kidney health using the patient’s overall pattern, repeated laboratory measurements, albumin in the urine, medical history, and other findings rather than a small group-level difference from one observational analysis.
The odds ratio also requires careful language. An adjusted odds ratio of 1.379 means that the highest tooth-loss group had higher odds of meeting the study’s eGFR threshold than the lowest group. It does not mean that 37.9% of those women developed kidney disease, and it does not tell us that tooth loss caused the difference.
The study therefore identifies a signal that researchers should investigate, not an effect size that should immediately change diagnostic criteria or treatment.
Why Might Tooth Loss and Kidney Function Appear Together?
Several explanations could produce the observed association, and more than one may operate at the same time.
Periodontitis can destroy the tissues and bone that support teeth and remains an important cause of adult tooth loss. It also involves a sustained inflammatory response. Previous systematic reviews have found an association between periodontitis and chronic kidney disease, although the evidence does not establish that periodontal disease independently causes CKD (Deschamps-Lenhardt et al., 2019; Chapple et al., 2025).
The relationship may also run in the opposite direction. Chronic kidney disease can alter immune function, inflammation, bone and mineral metabolism, nutrition, salivary conditions, and the patient’s ability to obtain or tolerate dental treatment. Those changes could worsen oral disease or make tooth retention more difficult.
Shared risk factors provide another explanation. Diabetes and hypertension strongly affect kidney health. Diabetes, smoking, aging, diet, income, and access to care can also influence dental disease and tooth loss. Statistical adjustment reduces some confounding, but it cannot remove every unmeasured difference or perfectly measure every included factor.
Finally, tooth loss can change chewing ability and food selection. People with extensive tooth loss may avoid fibrous foods or other nutrient-dense options that are harder to chew. However, the new study did not test whether tooth loss changed diet and then affected kidney function. That remains a plausible hypothesis rather than a demonstrated pathway.
What Do Oxidative Stress and Inflammation Add to the Story?
Among women, greater tooth loss correlated with a less favorable oxidative balance score and a higher systemic immune-inflammation index. The statistical analysis estimated that OBS accounted for 13.5% and SII for 4.1% of the association between tooth loss and eGFR (Gong et al., 2026).
Those percentages may sound mechanistic, but they require restraint. Mediation analysis works best when researchers can establish the order of events over time. Here, NHANES captured cross-sectional measurements. The analysis could not determine whether tooth loss preceded changes in OBS or SII, whether kidney dysfunction altered those measures, or whether another factor influenced all of them.
The oxidative balance score also included diet, smoking exposure, alcohol intake, physical activity, and body mass index. It did not directly measure oxidative damage in kidney tissue or periodontal tissue. Likewise, SII provides a broad blood-cell-based inflammatory marker rather than a specific measure of inflammation originating in the mouth.
The authors appropriately described these findings as potential indirect statistical associations. They offer hypotheses for longitudinal and mechanistic research, not proof that oxidative stress or inflammation carried an effect from tooth loss to kidney dysfunction.
Why Did the Association Appear Stronger in Women?
The sex-specific result is interesting, but the study cannot fully explain it. Biological differences in hormonal status, immune responses, oxidative balance, body composition, kidney physiology, and patterns of tooth loss could contribute. Social and behavioral differences in dental care, nutrition, health care use, and cumulative exposures may also matter.
Another possibility is statistical variation. Subgroup findings can emerge because of real biological heterogeneity, differences in measurement, residual confounding, or chance. The results need replication in prospective studies that prespecify sex-specific analyses and directly measure periodontal status, reasons for tooth loss, kidney damage, and changes over time.
Readers should not interpret the finding to mean that tooth loss matters only in women or that men with extensive tooth loss have no medical risk. It means that this study found clearer adjusted evidence in women than in men.
What Are the Study’s Most Important Limitations?
The cross-sectional design creates the central limitation. Because the researchers did not follow participants from healthy teeth and healthy kidneys through later changes, they could not establish temporal order or causation.
Tooth loss also represents a nonspecific outcome. Teeth may be absent because of periodontitis, decay, trauma, congenital absence, orthodontic treatment, pre-prosthetic treatment, dental access, cost, or patient and clinician decisions. A systematic review confirms that caries and periodontitis account for many adult extractions, but reasons vary across populations and clinical settings (Broers et al., 2022). NHANES did not provide the cause or timing of each missing tooth in this analysis.
The kidney definition presents another limitation. The researchers classified CKD using a creatinine-based eGFR below 60 mL/min/1.73 m². Clinical CKD assessment ordinarily considers persistence over time and may also use albuminuria or other evidence of kidney damage. A single survey measurement cannot confirm chronicity for an individual participant.
The investigators also omitted clinical periodontal status, dental-visit frequency, prosthetic rehabilitation, tooth location, and oral function. Counting missing teeth cannot show whether a participant had active periodontal inflammation, well-functioning dentures or implants, untreated decay, or a stable and healthy reduced dentition.
The handling of NHANES deserves particular attention. NHANES uses a complex, multistage sampling design, and properly weighted analyses can produce estimates representative of the civilian, noninstitutionalized U.S. population. The authors used a complete-case sample without survey weights, masked strata, or primary sampling units. They correctly stated that their estimates apply to the analyzed participants and that readers should not generalize them directly to the entire U.S. population (Centers for Disease Control and Prevention, 2026; Gong et al., 2026).
Finally, the extensive exclusions may introduce selection bias. Of the original 97,657 records, only 17,833 entered the final analysis, partly because the researchers limited the study to adults older than 40 and required complete data across many variables.
Does the Study Prove That Saving Teeth Protects the Kidneys?
No. Preserving natural teeth has clear benefits for chewing, communication, comfort, appearance, and quality of life. Preventing and treating oral disease remains worthwhile. But this study did not test whether periodontal treatment, restorative care, tooth retention, dentures, or implants improve eGFR or prevent CKD.
The reverse claim also remains unproven: the study does not show that kidney disease caused the observed tooth loss.
To answer the intervention question, researchers would need prospective trials or carefully designed longitudinal studies. They would need to establish baseline oral and kidney health, document the causes and timing of tooth loss, track periodontal treatment and oral rehabilitation, measure eGFR and albuminuria repeatedly, and account for changes in diabetes, blood pressure, medication use, smoking, diet, and access to care.
What Should Dentists and Patients Take From the Findings?
Extensive tooth loss should invite context, not alarm. A dentist who sees substantial tooth loss can ask about diabetes, hypertension, smoking, medications, medical follow-up, and the causes of the patient’s tooth loss. When a patient also has established kidney risk factors or has not received regular medical care, recommending a primary-care evaluation may be reasonable.
However, dentists should not present tooth loss as a CKD screening test. Many people lose teeth without having impaired kidney function, and many people develop CKD while retaining most or all of their teeth.
Patients should not request kidney testing solely because one tooth is missing. They can instead view oral health as one part of a broader health history. Someone with extensive tooth loss plus diabetes, hypertension, cardiovascular disease, a family history of kidney disease, or other medical concerns can ask a qualified clinician whether kidney evaluation is appropriate.
In my professional view, the strongest clinical message is collaborative rather than diagnostic. Dental findings sometimes reveal patterns of accumulated risk that deserve communication across dentistry and medicine. That does not turn the dental chair into a nephrology clinic. It means oral findings can help start a more complete conversation about health.
What Research Should Come Next?
Researchers need longitudinal studies that follow oral and kidney health over time. Future work should distinguish tooth loss caused by periodontitis from loss caused by decay, trauma, orthodontics, or treatment decisions. It should measure periodontal inflammation directly and include repeated eGFR, urinary albumin, and relevant kidney biomarkers.
Investigators should also apply the full NHANES survey design when they want population-level U.S. estimates. Independent cohorts can test whether the female-specific association replicates in different countries, age groups, and health care systems.
Most importantly, intervention research should ask whether preventing periodontal destruction or treating active periodontal disease changes kidney outcomes. Until such evidence exists, researchers should describe tooth loss as a possible marker of shared vulnerability rather than a demonstrated cause of kidney dysfunction.
Final Thoughts
The new study adds useful evidence to the growing literature on oral and systemic health. In 17,833 NHANES participants older than 40, greater tooth loss correlated with poorer estimated kidney function, with the clearest adjusted CKD association among women. The analysis also generated hypotheses involving oxidative balance and systemic inflammation.
Its limitations define what the finding means. Cross-sectional data cannot establish direction or causation. Missing teeth do not reveal why or when tooth loss occurred. A single creatinine-based eGFR threshold does not capture the full clinical definition of CKD. Unweighted analysis prevents direct national generalization.
The study therefore supports awareness, not a new diagnostic rule. Tooth loss may serve as one visible marker of cumulative health disadvantage, especially when it appears alongside diabetes, hypertension, smoking, older age, or limited access to care. Patients still need conventional medical assessment, and dentists should frame referrals around the full risk profile rather than the number of missing teeth alone.
Frequently Asked Questions
Does Tooth Loss Cause Kidney Disease?
The study does not establish that tooth loss causes kidney disease. It found an association at one point in time, so kidney dysfunction could precede tooth loss, tooth loss could precede kidney dysfunction, or shared factors could contribute to both.
Why Was the Association Stronger in Women?
The researchers found clearer adjusted categorical associations among women, but the study could not determine why. Biological, behavioral, social, and statistical factors may contribute. Other prospective studies need to replicate the result.
Should Everyone With Missing Teeth Get a Kidney Test?
No. Tooth loss alone does not diagnose CKD. People with extensive tooth loss and established risk factors such as diabetes, hypertension, older age, cardiovascular disease, or a family history of kidney disease can discuss appropriate evaluation with a medical clinician.
Can Dental Treatment Improve Kidney Function?
This study did not test treatment. Maintaining oral health offers important dental and quality-of-life benefits, but researchers still need intervention studies to determine whether periodontal treatment or tooth preservation improves kidney outcomes.
What Tests Assess Kidney Health?
Clinicians commonly use blood testing to estimate glomerular filtration rate and urine testing to assess albumin. They interpret those results with medical history, repeat measurements, medications, blood pressure, diabetes status, and other clinical information.
References
Broers, D. L. M., Dubois, L., de Lange, J., Su, N., & de Jongh, A. (2022). Reasons for tooth removal in adults: A systematic review. International Dental Journal, 72(1), 52–57. https://doi.org/10.1016/j.identj.2021.01.011
Centers for Disease Control and Prevention. (2026). Guidelines for high-quality analyses of NHANES data. https://wwwn.cdc.gov/nchs/nhanes/QualityAnalysesGuidelines.aspx
Chapple, I. L. C., Hirschfeld, J., Cockwell, P., Dietrich, T., & Sharma, P. (2025). Interplay between periodontitis and chronic kidney disease. Nature Reviews Nephrology, 21(4), 226–240. https://doi.org/10.1038/s41581-024-00910-5
Deschamps-Lenhardt, S., Martin-Cabezas, R., Hannedouche, T., & Huck, O. (2019). Association between periodontitis and chronic kidney disease: Systematic review and meta-analysis. Oral Diseases, 25(2), 385–402. https://doi.org/10.1111/odi.12834
Gong, L., Niu, L., & Zhao, W. (2026). Association between tooth loss and kidney function: Indirect roles of oxidative stress and systemic inflammation in NHANES 2001–2020. The Saudi Dental Journal, 38, Article 126. https://doi.org/10.1007/s44445-026-00232-1
Conflict of Interest
The author declares no conflict of interest relevant to this article.
Funding
The author received no external funding for this article.