High levels of white blood cells in the saliva of otherwise healthy young adults could serve as an early warning sign for cardiovascular disease, according to a recent study by researchers from Canada.

While white blood cell counts are a verified measure of oral inflammation, the team behind the investigation believe their findings could be used to develop a simple mouth rinse to routinely test for heart disease risk.

"The mouth rinse test could be used at your annual checkup at the family doctors or the dentist," says periodontist Michael Glogauer of the University of Toronto.

"It is easy to implement as an oral inflammation measuring tool in any clinic."

The periodontium – specialized tissue around the teeth that includes the gums – is packed with blood vessels. Gum disease can lead to changes in those blood vessels and is associated with increased risk of cardiovascular disease.

"We are starting to see more relationships between oral health and risk of cardiovascular disease," says lead author Ker-Yung Hong, a dentistry student who was at McMaster University at the time.

However it's unclear what effect mild levels of oral inflammation – experienced by many who appear healthy – have on heart health.

"If we are seeing that oral health may have an impact on the risk of developing cardiovascular disease even in young healthy individuals, this holistic approach can be implemented earlier on," Hong adds.

After fasting for at least six hours and only drinking water, 28 people aged 18 to 30 rinsed their mouths with tap water for 10 seconds, waited two minutes, and then rinsed again with sterile saline to provide saliva samples for white blood cell count.

The researchers then conducted a series of tests to evaluate each participants' risk of heart disease, including an electrocardiogram (ECG) to check their heart's operation and a measure of their resting blood pressure.

Since rigid, poorly functioning arteries are associated with an increased risk of developing cardiovascular disease, the researchers also conducted flow-mediated dilation to measure their ability to accommodate more blood flow, and an ultrasound to evaluate the stiffness of each volunteer's arteries.

On analysis of the results, the researchers found elevated white blood cell counts in the healthy young participants' saliva were linked to less healthy arteries and increased risk of cardiovascular disease.

Specifically, lower flow-mediated dilation was significantly associated with higher white blood cell counts in saliva. The researchers interpreted this as an increased risk of cardiovascular disease because it's an early indicator of poor arterial health.

But white blood cell counts did not correlate with pulse wave velocity, suggesting that the flexible structure of the arteries had not been damaged just yet.

"Even in young healthy adults, low levels of oral inflammatory load may have an impact on cardiovascular health — one of the leading causes of death in North America," says cardiovascular physiologist Trevor King from Mount Royal University.

The researchers suggested that when oral inflammation spreads to blood vessels in the body, it might impact the arteries' ability to produce nitric oxide, a gas that relaxes and widens the vessels, affecting blood flow.

It's a small study, but the results strongly suggest our oral health can be an indicator of our heart's function at any age, and dental hygiene has been linked to brain health too.

"Optimal oral hygiene is always recommended in addition to regular visits to the dentist, especially in light of this evidence," says King. "We are hoping to increase the study population and explore those results."

The study has been published in Frontiers in Oral Health.