Chronic kidney disease in older people: physiology, pathology or both?

The global population is aging due to a reduction in youthful deaths and an extension of the later stages of life. With aging comes a decline in the physiologic functions of various organs and systems. Vascular aging is associated with structural and functional changes of the arterial wall leading to loss of elasticity and compliance. Renal vasculature is not spared as aging is associated with arterial, arteriolar and capillary, glomerular changes (glomerulosclerosis). It is likely that age-related vascular changes are linked to the decline in renal function observed with aging. These changes occur at varying stages of aging depending on predisposing genetic factors and associated life course exposure to cardiovascular risk factors including hypertension and diabetes. The decline in renal function with 'normal' aging in the absence of associated progressive cardiovascular disease is slow and does not seem to be of major clinical significance. The current definition of chronic kidney disease (CKD), including microalbuminuria, and the method of estimation of glomerular filtration rate have inadvertently resulted in an exaggerated prevalence of CKD in the elderly. This is combined with the fact that most of the studies showing decline in renal function with aging are limited by the absence of a correction for associated comorbid confounding factors, resulting in difficulty separating the effect of physiological aging on kidney function from pathological aging due to comorbidities. Such a correction is difficult, if not impossible, to objectively construct. We suggest that only those fractions of older patients with underlying progressive vascular pathology likely to involve the kidneys will, in the future, warrant attention to reduce vascular risk and the associated kidney damage.