Kidney function is critical to health, but, as is the case for all organs, the kidneys declines with age. The damage of aging produces harmful outcomes in many ways. For example, hypertension causes structural pressure damage in sensitive tissues in the kidneys. Further, senescent cells and other sources of chronic inflammation disrupt normal tissue maintenance processes in the kidneys, leading to the scar-like collagen deposits of fibrosis. In turn, loss of kidney function accelerates many other aspects of aging, including neurodegeneration and the onset of cognitive decline.
An international study that has been carried out on nearly 3000 people in Norway, Germany, and Iceland, shows that our kidney function deteriorates with age, even if we do not have any other diseases. One of the groups that have participated in the study consists of over 1600 people and stems from the Tromsø Study, which is Norway's most comprehensive and best participated population study throughout 40 years. This group has been through the different examinations three times; between 2007 to 2009, 2013 to 2015, and 2018 to 2020.
"What we see is that what happens in our kidneys when we age is representative of all the other things that happen in our bodies. The kidney function deteriorates, not because we get ill, but as part of ageing. Loss of kidney function is something that happens to all humans and is thus a way to determine ageing in general. There is still variation as to how quickly this happens, and we still do not have good answers as to why this variation occurs. We have examined many factors that can play a part as to why some of us experience larger loss of kidney function than others."
The researchers use a precise method of measuring kidney function. They inject a substance into the blood veins that only separates into the kidneys, and let a few hours pass before they measure how much of the substance remains in the blood. This gives a measure of the kidney's ability to remove toxins and waste products. Researchers explain that more people may experience loss of kidney function as it becomes more common to survive diseases like cancer and heart and vascular diseases.