Bleeding gums may be more than a dental problem. A large German study suggests that people with severe gum disease could also face a higher risk of early kidney damage, adding to growing evidence that the health of the mouth and the rest of the body are closely connected.

Researchers from the University Medical Center Hamburg-Eppendorf found that severe periodontitis—a long-lasting infection that harms the gums and the bone around teeth—was directly connected to worse kidney function and higher amounts of protein in urine, which is the gums and the bone supporting teeth, and was independently linked with poorer kidney function and higher levels of protein leaking into urine, an early sign of kidney disease. Their findings were published on April 6, 2026, in the International Journal of Oral Science.

The team analysed health data for 6,179 adults enrolled in the Hamburg City Health Study in Germany. Participants underwent detailed dental examinations using the internationally recognised 2017 American Academy of Periodontology/European Federation of Periodontology (AAP/EFP) staging system. Researchers then checked kidney health by looking at the estimated glomerular filtration rate (eGFR)—a blood test that shows how well the kidneys are cleaning waste—and the urinary albumin-to-creatinine ratio (uACR), which finds small amounts of protein in urine that could indicate early kidney damage.

"We aimed to evaluate the relationship between periodontitis and markers of early kidney dysfunction, including reduced renal function and albuminuria, and to explore the potential mediating role of systemic inflammatory markers," said Dr Christian Schmidt-Lauber, explaining the purpose of the research.

The findings revealed a clear pattern. Severe gum disease was found in 14% of people with normal kidney function but rose sharply to 36% among those with moderately reduced kidney function. As kidney health got worse, tooth loss and damage to the tissues that support teeth became more common.

Importantly, the association remained even when the researchers adjusted for age, sex, diabetes and smoking, suggesting that gum disease itself may contribute to the risk rather than simply sharing common risk factors.

The scientists also measured two markers of body-wide inflammation—high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6). Both increased as gum disease and kidney impairment became more severe. However, inflammation explained only part of the relationship. The researchers believe other biological processes, including the spread of harmful oral bacteria into the bloodstream, damage to blood vessel linings and increased oxidative stress—an imbalance that can injure cells—may also play important roles.

"By demonstrating an association between periodontitis and markers of early kidney dysfunction, this study highlights oral health as a potential window into kidney health," said Prof. Dr Ghazal Aarabi.

The findings echo previous research published in journals, including the Journal of Clinical Periodontology, and guidance from organisations such as KDIGO, which have increasingly recognised links between chronic inflammation and kidney disease. However, the researchers stressed that this study shows an association, not proof that gum disease directly causes kidney damage.

Because chronic kidney disease (CKD) often develops silently until substantial damage has occurred, the researchers say routine dental care may one day help identify people who could benefit from earlier kidney screening. They also call for clinical trials to determine whether treating severe gum disease can slow the decline in kidney function.