[The definition of chronic kidney disease in a context of aging population].

Chronic kidney disease (CKD) is a progressively chronic disease that carries a high burden of morbidity and mortality and is associated with significant healthcare utilization and costs. Recent trends shown that the prevalence of CKD is stable in Europe and USA, whereas tends to decline in some countries with a high standard of care. According to international guidelines, chronic kidney disease (CKD) is defined as the presence of kidney damage or a glomerular filtration rate (eGFR) less than 60 ml/min. This staging method has a main drawback, its imprecise assessment of renal function at the extremes of the age bracket: the use of a fixed threshold value (glomerular filtration rate [GFR <60 ml /min]) to define chronic renal failure appears an imprecise measure in the young and in the elderly. In these two groups, in fact, the measurement of GFR is difficult to categorize in a "rigid" system of classification. The reduction of the GFR with aging is due to a complex process that leads to a steady reduction of the functioning nephrons over 40 years of age. Taken together, these findings should spur us to adopt a new definition of CKD. An age-adapted definition of CKD could be a good solution to avoid a diagnosis of CKD in elderly patients (GFR >45 ml/min) when there are no prognostic implications on survival. The adoption of this new definition would also reduce the high prevalence of the disease in the general population, with a beneficial reduction of the costs associated with monitoring a mildly decreased eGFR.