Many young Canadians in the 'grey zone' when it comes to kidney function. Here's what that means for their health

A new Canadian study published in the British Medical Journal suggests that even a small reduction in kidney function could result in poor health outcomes for young people.

Researchers surveyed health records from eight million people in Ontario from the Institute for Clinical Evaluative Sciences (ICES) between 2008 and 2021. The research focused on adults aged 18 to 65 who had at least one test for kidney function but no history of kidney disease.

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Of the participants, 18 per cent between the ages of 18 to 39 had kidney function somewhat "below normal levels" but not enough to trigger the threshold of having chronic kidney disease.

Dr. Manish Sood, the senior researcher of the study and kidney specialist at The Ottawa Hospital and the University of Ottawa, says patients in this group are in the "grey zone."

"We showed in young people 18 to 39 even a slight decline — 25 per cent or more — in that gray zone is associated with what we call adverse clinical events: heart disease, accelerated risk of kidney failure, and even a risk of death," Dr. Sood told CTVNews.ca in an interview Wednesday.

WHO IS AT RISK?

Kidneys balance the electrolyte composition in bodies, and also control blood pressure and secrete vitamin D and erythropoietin (types of hormones.)

Over a person's life their kidney function will decrease. Sood says this is normal, but this study showed that many younger Canadians are seeing early decreases in their kidney function that are not being caught or monitored.

The study says young Canadians with a 20 to 30 per cent loss in kidney function are associated with a 1.4-fold increase in death, a 1.3-fold increase in a cardiac event and a six-fold increase in the risk of kidney failure.

However, the absolute risk of any of these events was still low at less than two per 1000, the press release states.

Sood worries that due to the high threshold of chronic kidney disease at 60 per cent function for all people, it could be too high to take preventative measures.

"What they should do is these people should be monitored, have tests repeated," he said. "If it persists, they need to be evaluated, maybe sent to a specialist."

Nearly one in 10 Canadians have a type of kidney disease, which do not show symptoms until it's extremely severe, the Kidney Foundation of Canada states.

The registered charity says a person can lose more than 50 per cent of their kidney function before symptoms appear.

"(Does) one age fits all definition, 60 per cent across the board, (work) is the question," Sood said. "If we're in the prevention focus we want to prevent people from developing kidney disease when they're 65 and 70. Maybe this is the important first signal and step."

A number of factors can put people at risk of developing chronic kidney disease but the most common, Sood said, are high blood pressure and diabetes. This can be mitigated by living a healthy lifestyle and not smoking.

When a kidney has lost some function there is no way to rehabilitate it, he said.

"More work needs to be done to tease out among these young adults who have slightly low risk, what is the exact cause? Who are the highest-risk groups," Sood said.

HOW TO CHECK FOR KIDNEY FUNCTION

In Canada the blood test for kidney function is routinely available and common, Sood said, but there are barriers to accessing it.

"It's controversial whether we should be screening everybody," he said.

A previous study Sood was involved looked into whether doing kidney tests on everyone would be cost-effective. The survey concluded that universal testing was not cost-effective, which is why doctors recommend it to only those who are at high-risk.

"But there is some emerging data from the States that's challenging that now," he said. "So it may shift in the years to come, where a broader number of people will have a test done."

The Canadian study also showed after one test, less than half of people were tested again.

"It should be repeated in kind of a perfect situation," Sood said. "They should have a urine test. And the reason is to make sure because there are no urine abnormalities which is a sign that these people are at a modified increased risk."

The study shows that less than five per cent of people who had a kidney test had a urine test as well.

KIDNEY FUNCTION CALCULATOR

Without access to testing, Sood said patients can use an online calculator which he helped develop.

By answering simple lifestyle questions, the quiz can tell people if they could be at risk of developing chronic kidney disease, although Sood says it may need to be modified after seeing the new research,.

"The risk calculator is predicting 60 or lower, in other words early chronic kidney disease," he said. "Now we've got to think, 'Well, should we re-modify this calculator to be 25 per cent decline for younger people?'"

Although the study is pointing to risks in young people, Sood is hopeful more research can help increase awareness of kidney function for all Canadians.

"That's why this kind of early detection ideas are so important because we have things to slow it down once the process starts," he said.