(RxWiki News) There are several ways to measure kidney function. A couple of these measures were thought to increase as people grew older. Now it looks like signs of poor kidney function are not just part of the aging process.
In a recent study, low estimated glomerular filtration rate (eGFR) and high albuminuria - two signs of poor kidney function - were associated with kidney failure and death in people of all ages.
According to the research authors, this study showed that markers of chronic kidney disease were associated with risk across all ages.
"If you have diabetes or heart disease - get tested for kidney issues."
"Chronic kidney disease affects 10 to 15 percent of adults in the United States, Europe and Asia," said Stein I. Hallan, MD, PhD, of the Norwegian University of Science and Technology, and colleagues in background information to their study.
Rates of kidney disease increase dramatically with age, they added.
It has been suggested that chronic kidney disease should be defined by eGFR (how much blood passes through the kidney's filters) and levels of albuminuria (having too much protein in the urine). However, researchers are unclear about whether these two measures of kidney function change with age.
That is, older adults may have low eGFR and high albuminuria without the same risks as younger people.
Dr. Hallan and colleagues set out to study how age might affect the risks associated with low eGFR and high albuminuria. The researchers looked specifically at the risks of end-stage renal disease (total or near-total kidney failure) and death.
Both low eGFR and high albuminuria were associated with a risk of end-stage renal disease and death regardless of age across a wide range of populations.
In addition, low eGFR increased the risk of death at all ages, but the magnitude of this excess risk was less in the elderly.
The pattern was similar but less noticeable for patients with high albuminuria versus those with lower albuminuria. Patients with higher albuminuria had a higher risk of death than those with lower albuminuria. Again, the risk gap between high and low albuminuria became smaller as people grew older.
When it came to the absolute risks, low eGFR and high albuminuria were associated with higher rates of death, particularly for older people.
Results also showed that the risk of end-stage renal disease associated with lower eGFR and higher albuminuria was similar across all age groups.
"Our findings have several important implications," the authors said.
First, the study showed that kidney measures used for defining and rating chronic kidney disease are strong predictors of risk for all age groups, even those 75 years of age and older. This goes against the view that low eGFR is just a normal part of aging.
Second, the findings suggest that measures of kidney disease should be used as part of measures of death risk. However, this potential use needs more research, the authors said.
Third, the higher death rates among older patients suggest that low eGFR and high albuminuria is not a normal part of aging. Rather, they are signs of risk. As such, "older adults should not be left out from management strategies of chronic kidney disease," the authors said.
"Our data support a common definition and staging of chronic kidney disease based on eGFR and albuminuria for all age groups," they concluded.
The study included more than 2 million participants from around the world.
The risk of death for lower eGFR versus higher eGFR for each age group was as follows:
- hazard ratio of 3.50 for 18 to 54 year olds
- hazard ratio of 2.21 for 55 to 64 year olds
- hazard ratio of 1.59 for 65 to 74 year olds
- hazard ratio of 1.35 for those 75 years of age and older
A hazard ratio explains how much an event happens in one group versus another. A hazard ratio of more than 1.0 means the event happens more in the first group than in the second.
The risk of death for high albuminuria versus lower albuminuria for each age group was as follows:
- hazard ratio of 2.53 for 18 to 54 year olds
- hazard ratio of 2.30 for 55 to 64 year olds
- hazard ratio of 2.10 for 65 to 74 year olds
- hazard ratio of 1.73 for those 75 years of age and older
For each age group, low eGFR was associated with the following amount of excess deaths per 1,000 person-years:
- 9.0 excess deaths for 18 to 54 year olds
- 12.2 excess deaths for 55 to 64 year olds
- 13.3 excess deaths for 65 to 74 year olds
- 27.2 excess deaths for those 75 years of age and older
For each age group, high albuminuria was associated with the following amount of excess deaths per 1,000 person-years:
- 7.5 excess deaths for 18 to 54 year olds
- 12.2 excess deaths for 55 to 64 year olds
- 22.7 excess deaths for 65 to 74 year olds
- 34.3 excess deaths for those 75 years of age and older
The study was published October 30 in the Journal of the American Medical Association (JAMA).
The research was supported in part by the National Kidney Foundation, which receives some funding from the pharmaceutical companies Abbott and Amgen.
Some of the study's authors reported receiving grant support from the National Kidney Foundation, National Institutes of Health and the Netherlands Organization for Scientific Research. Authors also reported potential conflicts of interest with pharmaceutical companies Amgen, Pfizer, Sanofi-Genzyme, Bayer, Baxter, Abbott, Merck and Roche.