A new Canadian study published in the British Medical Journal indicates that even a slight decline in kidney function can lead to poor health outcomes for young people.

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

Among the participants, 18% of those aged 18 to 39 had somewhat below normal kidney function, but not enough to qualify as chronic kidney disease.

Dr. Manish Sud, the lead specialist researcher on the study and kidneys at Ottawa Hospital and the University of Ottawa, said in an interview with CTV News, "Patients in this group are in the gray area," noting that the study showed 25% of young people aged 18 to 39 experience mild kidney function decline, meaning they are in that gray area, associated with what we call adverse clinical events such as heart disease, risk of accelerated kidney failure, and even risk of death.

The kidneys balance the body's electrolyte composition, control blood pressure, and secrete vitamin D and erythropoietin (types of hormones). Dr. Sud says that over a person's lifetime, kidney function will decline, which is normal, but this study showed that many younger Canadians experience early declines in kidney function that go undetected or unmonitored.

The study says young Canadians who lose 20 to 30% of kidney function are associated with a 1.4 times increase in mortality, a 1.3 times increase in heart conditions, and a sixfold increased risk of kidney failure.

However, the absolute risk for any of these events remains low at less than two per 1,000, as stated in the press release. Sud fears that due to the 60% increase in the threshold for chronic kidney disease for all people, taking preventive measures might be too high.

Sud said, "What they should do is that these people should be monitored and testing repeated, and if kidney function continues to decline, it should be assessed and possibly referred to a specialist."

Nearly one in ten Canadians has some form of kidney disease, which shows no symptoms until it becomes very severe, according to the Kidney Foundation of Canada. The foundation states that a person can lose more than 50% of kidney function before symptoms appear.

Sud explained that there are several factors that can put people at risk of chronic kidney disease, but the most common are high blood pressure and diabetes. This can be mitigated by following a healthy lifestyle and not smoking, stressing that when the kidney loses some of its functions, it cannot be rehabilitated.

Sud said, "More work is needed to follow up on these young people who have slightly low risks, what is the exact reason? Who are the most vulnerable groups."