Researchers and clinicians are increasingly examining oral health as a significant factor in wider systemic disease, with emerging evidence linking gum disease and chronic oral infections to cardiovascular disease, diabetes, stroke, arthritis and cognitive decline.

The growing body of research is also challenging the longstanding separation between dentistry and mainstream medicine, a divide rooted in the historical development of dentistry as a trade distinct from clinical medicine.

While dentists and physicians continue to train and operate through separate professional systems in many countries, including the United Kingdom, scientists say the biological relationship between oral health and the rest of the body is becoming more difficult to ignore.Steve Kerrigan, professor of precision therapeutics at RCSI University of Medicine and Health Sciences in Dublin, said the mouth functions as a direct pathway into the body’s circulatory and respiratory systems.

The human mouth hosts roughly 700 bacterial species, many of which are harmless under normal conditions but can become problematic when oral hygiene deteriorates.Gum disease remains one of the most common chronic inflammatory conditions globally. In the UK, around half of adults are estimated to experience some form of the disease.

Gingivitis, the early and reversible stage, is typically identified through bleeding during brushing or flossing. Periodontitis, a more advanced form, involves inflammation severe enough to detach teeth from the gums and is considered irreversible.“Gum disease is now classed as a chronic inflammatory condition in its own right,” Kerrigan said, comparing it to illnesses such as asthma, chronic obstructive pulmonary disease and Crohn’s disease.

Research into cardiovascular complications has become one of the most developed areas in the field of oral-systemic health. According to Kerrigan, several studies have shown that a large proportion of patients with cardiovascular disease also exhibit gum disease, although scientists continue to investigate whether oral disease directly causes cardiovascular conditions or acts alongside broader health factors.

One major focus is atherosclerosis, a condition in which cholesterol, fat and calcium accumulate on artery walls and restrict blood flow. Researchers have identified oral bacteria within atherosclerotic plaques, raising questions about whether bacteria from diseased gums contribute directly to plaque formation or become embedded after arterial damage has already occurred.

Scientists have also examined the role of oral bacteria in clot formation. Kerrigan said bacteria entering the bloodstream through bleeding gums or untreated dental infections can interact with platelets, the blood components responsible for clotting. That interaction may trigger the formation of clots capable of obstructing blood vessels.

“When these bacteria bind to platelets, it causes them to stick together the exact same way as when you cut yourself,” Kerrigan said. He added that clots reaching vessels in the brain may contribute to transient ischemic attacks or strokes, while clots affecting coronary circulation can increase heart attack risks.The same bacterial mechanisms have also been associated with infective endocarditis, a potentially serious condition involving inflammation of the heart’s inner lining and valves.

Patients with replacement heart valves have long received preventative antibiotics before invasive dental procedures because oral infections are already recognised as a source of bloodstream infection.Diabetes has emerged as another area where oral health appears closely connected to wider metabolic function.

Researchers increasingly describe the relationship as bidirectional. Chronic gum inflammation may interfere with blood sugar regulation, while persistently elevated glucose levels in diabetic patients can increase vulnerability to gum disease.A 2025 study cited by researchers found that patients undergoing root canal treatment experienced reductions in blood sugar, cholesterol and fatty acid levels after infected dental pulp was removed and sealed.

The findings suggested that treatment of severe dental infection could have broader metabolic benefits beyond preserving teeth.Kerrigan said mortality risks are significantly higher among patients who experience both diabetes and advanced gum disease compared with diabetic patients without severe periodontal problems.

Researchers are also investigating potential links between oral inflammation and degenerative or inflammatory conditions affecting other parts of the body. Studies referenced by Professor Kang found statistical associations between gum disease and worsening arthritis symptoms, particularly among patients with arthritic knees.

Kang said poor oral health can also affect psychological wellbeing and social behaviour. Pain, visible dental deterioration and chronic inflammation may reduce confidence and increase social withdrawal, while medications used to manage broader health conditions can reduce saliva production and further damage oral health.“Everything is interlinked,” Kang said.Researchers caution, however, that many findings remain based on population-level statistical analysis rather than direct prediction for individuals.

Experts stress that the existence of associations between oral disease and other illnesses does not mean isolated symptoms necessarily indicate severe future illness.“It does not apply to individuals,” Kang said, adding that occasional bleeding while brushing should not automatically be interpreted as evidence of future dementia or major disease.

The debate over oral health is unfolding amid mounting concerns over access to dental care, particularly in the UK’s National Health Service system. The government’s most recent oral health survey, published in 2021, found that around one-quarter of adults with natural teeth reported damaged, cracked or broken teeth, fillings or crowns.

At the same time, shortages of NHS dental appointments have led to reports of patients delaying treatment, self-medicating or attempting to remove damaged teeth themselves.Researchers say tooth loss may also alter the mouth’s microbiome, potentially affecting digestion and wider biological processes.

Kerrigan noted that oral bacteria play a role in the early stages of digestion, making long-term disruption to the oral environment a broader health concern.Dental specialists continue to emphasise basic preventive measures as the most effective strategy for reducing risks associated with oral disease.

Regular brushing, flossing and limiting sugar intake remain central recommendations.Kerrigan said electric toothbrushes with rotating heads may improve plaque removal compared with manual brushing. He also warned that frequent snacking on sugary foods can increase bacterial growth and accelerate gum and tooth damage.

Scientists say oral health should be viewed as part of broader preventive healthcare rather than as an isolated cosmetic issue.

Researchers note that individuals maintaining strong overall health habits often also demonstrate better oral hygiene practices, reflecting what they describe as an increasingly interconnected understanding of human health.

The analysis of almost 1.2 million people by Israel’s largest healthcare provider will offer further hope for countries as they get shots into citizens’ arms, particularly those considered vulnerable, and curb the pandemic that has killed more than 3.1 million people.

The vaccine was 80% effective against symptomatic infection for people with heart or chronic kidney diseases, 86% for people with type 2 diabetes, 75% for cerebrovascular disease, and 84% for people suffering from immunodeficiency, according to the Clalit Research Institue study.

For people who were vaccinated and were already suffering three or more chronic conditions or risk factors, such as heart disease, neurological disease, chronic kidney disease, chronic lung disease, smoking, pregnancy or obesity, the research shows it was 88% effective in preventing symptomatic infection.

It was more than 90% effective against severe disease for people with type 2 diabetes, heart or cerebrovascular disease and 100% for people suffering from immunodeficiency.

The data is the latest from Israel where a universal and digitised healthcare system and the speedy vaccination programme have allowed researchers insights into the vaccine’s potency. Clalit covers more than half of Israel’s population.

The results were lower than the 96% overall vaccine effectiveness seven days or more after the second dose, found by the study and the 95% effectiveness found in clinicial trials last year.

But researchers said they offered some optimism that the vaccine still offers protection against severe illness in people who become infected after they get their shots.

“Protection is mildly reduced among patients with several co-morbidities. These results are very encouraging, as they suggest that most COVID-19 cases will be prevented by vaccination even in the elderly and chronically ill,” said Ran Balicer, Clalit’s chief innovation officer.

“People with chronic diseases, multiple chronic or severe chronic diseases, should get vaccinated because the vaccine is very effective in protecting them against the high rates of complications that are expected,” Balicer said.

The research was also carried out by Harvard and the University of Michigan and published in the New England Journal of Medicine on Thursday.

The Clalit study, compared 596,618 people vaccinated between Dec. 20 2020 and Feb. 14 against the same size group of unvaccinated people, matching age, gender and other characteristics.

The subgroup of the people with chronic diseases was about 130,000 people, Balicer said.

More than half of Israel’s 9.3 million population has been fully inoculated since its vaccination drive began in late December. COVID-19 cases have dropped continuously since a mid-January peak as the economy has largely opened.

Until mid-April, Israel has documented 98% fewer coronavirus cases, 93% fewer critically ill and 87% fewer COVID-19 deaths, according to Eran Segal, data scientist at the Weizmann Institute of Science.

Balicer said that although Israel was not yet at “herd immunity,” the sharp drop was “proof of the potential of mass vaccination to really take us out of harm’s way and shows the light at the end of the tunnel”.

Obesity, Hypertension and Overweight

The large sample size allowed researchers to look more closely at subgroups of people with specific chronic diseases which would not necessarily be examined in a vaccine clinical trial, the researchers said.

It also found the vaccine to be 92% effective in preventing symptomatic COVID-19 among people over the age of 70, 96% for overweight people and 93% for those suffering obesity and provided 90% protection for people suffering from hypertension.

Danny Altmann, an immunology professor at the Imperial College London, said the study was among the first real world research to offer such granular data into vaccinated subgroups.

“Transitioning into real-world application, the effectiveness still looks terrific, but inevitably there are people who make poor vaccine responses,” he said in an email to Reuters.

“We need to know who they are, why, and what can be done to rescue immunity. Next, we need to see the results from each of the big cohort studies for the various patient groups.”

The U.S. Centers for Disease Control and Prevention (CDC) Director Rochelle Walensky said that of the 84 million people who have been fully vaccinated in the United States, fewer than 6,000 have got sick with COVID-19 more than two weeks after being fully dosed.

Of those, nearly 400 were hospitalised and around 75 died, according to CDC data. Some of the hospitalisations and deaths were not due to COVID-19 infections.

Pfizer’s late-stage clinical trial included people with co-morbidities. The most frequently reported co-morbidities were obesity (35.1%), diabetes (with and without chronic complications, 8.4%) and pulmonary disease (7.8%), a spokesman said.

The health authorities have identified one of their top concerns as they wage war on diabetes: white rice. It is even more potent than sweet soda drinks in causing the disease.

Sharing his battle plan to reduce the risk of diabetes, Health Promotion Board chief executive Zee Yoong Kang said that obesity and sugary drinks are the major causes of the condition in the West.

But Asians are more predisposed to diabetes than Caucasians, so people do not have to be obese to be at risk. Starchy white rice can overload their bodies with blood sugar and heighten their risk of diabetes.

Mr Zee is armed with data. A meta- analysis of four major studies, involving more than 350,000 people followed for four to 20 years, by the Harvard School of Public Health – published in the British Medical Journal – threw up some sobering findings.

One, it showed each plate of white rice eaten in a day – on a regular basis – raises the risk of diabetes by 11 per cent in the overall population.

Two, it showed that while Asians, like the Chinese, had four servings a day of cooked rice, Americans and Australians ate just five a week.

But Mr Zee does not plan to ask Singaporeans to stop eating rice, a popular feature of meals here. What he would like is to see more people turn to healthier varieties.

Long grain white rice is also better than short grain when it comes to how it spikes blood sugar – a rise in sugar levels causes the pancreas to produce more insulin, and frequent spikes can lead to diabetes.

He would also like people to try adding 20 per cent of brown rice to their white rice. This amount is enough to reduce their risk of diabetes by 16 per cent.”There is no need to fully replace what they now eat. Just increase the quantity of whole grain and brown rice.”

Health Minister Gan Kim Yong said last month that this disease is already costing the country more than $1 billion a year. Diabetes is a major cause of blindness, kidney failure and amputations in Singapore.

Dr Stanley Liew, a diabetes expert at Raffles Hospital, advised people to eat less rice. He added that most junk food and sodas are just as bad and should be discouraged.

Article first published on Singapore-based Straitstimes.

Salma Khalik is senior health correspondent for Straitstimes with three decades of jounalism experience.