a little loss of kidney function could carry big health risks: study

health professionals have long believed that healthy, young adults don’t need to worry about kidney function unless it drops to about 50 per cent of normal levels. but new research indicates as little as a 20 to 30 percent reduction could drastically increase the risk of adverse outcomes, like death, cardiovascular events and kidney failure.

a little loss of kidney function could have major future risks: study
one in 10 canadians are living with kidney disease, according to the kidney foundation of canada. ben schonewille/getty images

chronic kidney disease is often called the “silent killer” because, like an assassin, it sneaks up on you without warning. one minute you’re feeling fine, the next you’re coping with a life-threatening condition. but the kidneys are such hard-working little organs that health professionals have long believed that healthy, young adults don’t need to worry about kidney function unless it drops to about 50 per cent of normal levels.

new research out of the ottawa hospital, however, challenges that line of thinking.

researchers for the study, published in the british medical journal , analyzed health record data collected between 2008 to 2021 by the institute for clinical evaluative sciences (ices) of more than eight million adults in ontario aged 18 to 65 who had at least one blood test for kidney function but who had no history of kidney disease.

in the 18-to-39-year age group, 18 per cent had modestly low kidney function but not low enough to be diagnosed with chronic kidney disease. still, for these individuals, a 20 to 30 percent loss in kidney function was associated with a 1.4-fold increase in death, 1.3-fold increase in a cardiac event, and a 6-fold increase in kidney failure , according to a news release.



the overall risk of any of these events, however, was less than two per 1,000.

but it is a wake-up call for all canadians, since one in 10 of us are living with kidney disease, according to the kidney foundation of canada . and although we may not notice it creeping up on us, the first signs and symptoms we should be aware of can include fatigue, loss of appetite, itching, nausea and shortness of breath. the good news is, a simple blood test is all it takes to put your mind at ease. the bad news is, such a test is not routinely offered.

healthing spoke with dr. manish sood, senior scientist, nephrologist and jindal research chair for the prevention of kidney disease at the ottawa hospital, professor at the university of ottawa, and senior author of the study to tell us more about the implications of the research, and how canadians — especially young canadians — can evade the silent killer.

how did this study on kidney disease come about?

as we age, our kidney function naturally declines. it’s highest when we’re young adults and lower when we get towards 80, 85. but the definition of early chronic kidney disease is the same for all ages. a healthy young person [has] a [normal] kidney function level of about 100. at around 60, we start calling it early chronic kidney disease, so you have to lose a lot before it’s even recognized. and the reason we didn’t recognize it is that it was a grey zone. in this 60 to 100 [range], we didn’t know if there was an increased risk of any problems at, say, 77.

so, previously, if a young person’s decline was about 20 per cent, a doctor would not discuss it with the patient?



no, because no one knew that it mattered. so imagine you’re a healthy 24-year-old with a normal [kidney function] level of about 110 and you felt fine but had a test and it was 84. your doctor may choose to repeat it, or may think it’s not kidney disease. and that’s the point: that this is not even recognized. and it’s nobody’s fault, it’s just that we didn’t know there was a risk. it’s hard to study young people because they don’t often have heart attacks. you need these mega data sets to study them.

is kidney disease among young adults on the rise?

kidney disease is on the rise, as is heart disease, in young people. a lot of it is due to increase in obesity, diabetes and high blood pressure. the same factors that drive heart disease drive kidney disease.

so your study results have real world implications for both younger populations and health professionals?

exactly. and we only had data for 10 years, so you can imagine if we had data for 40 years, the signal would likely be way stronger. because if we’re looking at a 23- year-old who has low kidney function for 10 years, the chances of them having a heart attack are really low. but it’s likely if they have something wrong in their kidneys now, they may have it in their 50s and 60s. that’s the worrying part. our average lifespan in canada is 80 years, so if we see even a small signal in a short time frame, there’s probably going to be a real big one down the road.

so earlier interventions are critical?



that’s what this study says: that this is serious, we need to focus on this now. it says we should at least monitor it. the minimum we should do is repeat these tests in these people, see if they have any heart disease risk factors, because the number one killer of people with kidney disease is premature heart disease. and they should give a urine sample to see if there’s anything that’s causing further risk factors for kidney disease to be worse.

if young people generally don’t get these kinds of tests, yet you had access to a vast data set from young adults, why were they getting these tests?

if they had an annual check-up, if that even exists now, [doctors] don’t just send off this blood work in young people, so there would have to have been testing for something suspicious. [a kidney test is] one of the most basic blood tests, so if somebody is getting any blood test it would likely be attached to it. there are four million people between the ages of 18 to 39 [in the study], and when we look at the average level of kidney function in that group, it’s normal. we even looked at people without diabetes, without a history of high blood pressure. we tried to interrogate it in a lot of different ways to see the most normal version of them.

how can people with a reduction in kidney function ward off future serious health issues?



the first [recommendation] is to monitor, have things repeated, talk to your doctor, get urine tests done. the second is, if you fall into this category, it would be good sound advice to have a healthy lifestyle. so if you’re a smoker, quit, if you drink alcohol, cut back, try to have a good diet and exercise. those are easy interventions that can be done while you figure out if a medication would help.

based on the study showing that even a modest drop in function is concerning, is the message different now?

yes. that traditional message [that it was not a concern until it dropped to 50] was based on studies that were done, all meaningful but not as big, and the age cut off was not that granular. it clumped 18-to-50-year-olds together [so you couldn’t] see a signal. we broke them down into smaller groups and looked at detailed decreases in kidney function — 5 per cent, 10 per cent, 20 per cent — and that’s how we found these signals. so yes, now the message has to change. a decline of even 25 per cent or more is meaningful and has consequences.

what do most people misunderstand about kidney disease?

that it’s silent, and silent right to the end. a lot of people think they’ll wait until they see symptoms, but they don’t get it. when i tell patients they have chronic kidney disease based on blood work, they say, ‘well, i don’t have back pain.’ that shows you that awareness is very low. back pain is not associated with chronic kidney disease. it could be a urinary tract infection or kidney stones. blood work is the only [way to confirm].

do you foresee a future when kidney tests will be routine for younger adults, regardless of risk?



no. about 10-plus years ago we did a study where [we found that] screening a whole population wasn’t a cost- effective strategy, so we only screened people at risk. but now this may be changing. it may lead to [a policy where] everybody should be screened at certain levels. but when, where, how often and how best to do it is all to be determined. we need to get to a point where there are technologies [that will allow for] more screenings, and cheaper, easier methods so we can catch these conditions earlier.

where do you go from here?

future studies. some of the immediate things we want to do is [look at] the sequence of events that may link reduced kidney function as a young adult to heart disease. it used to be thought that high blood pressure damages the kidneys over time, now it may be the other way around. younger people who have reduced kidney function may be actually driving hypertension, and that’s the link to heart disease.
robin roberts is a vancouver-based writer.
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