The prevalence of CKD rises dramatically with age. Based on the results of the National Health and Nutrition Examination Survey 1999-2004 (NHANES), more than one third of those aged 70 or older have moderate or severe CKD defined as an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2
]. While all stages of CKD are more common at older ages (including earlier stages of CKD, defined as albuminuria with a preserved eGFR), it is the prevalence of moderate CKD (eGFR 30-59 ml/min/1.73 m2
) that increases most dramatically with advancing age ().
Prevalence of CKD by age and stage (source Coresh et al, JAMA, 2007), requires copyright.
The high prevalence of CKD in the elderly no doubt reflects the presence of a variety of different risk factors for CKD such as diabetes and hypertension in older individuals. However, high rates of CKD in the elderly may also occur because of an age-associated decline in kidney function that is not explained by other known risk factors. Relatively little is known about how renal function changes during the course of “normal” aging. The Baltimore Longitudinal Study of Aging (BLSA) measured change in creatinine clearance over time among a subset of participants without kidney disease or other known comorbidities [3
]. Among these participants, creatinine clearance declined on average by 0.75 ml/min/year. However, among some participants in this study, renal function did not decline at all. Results from BLSA thus suggest that on average kidney function tends to decline with aging even among those without comorbidity, but that this decline does not appear to be inevitable.
Regardless of the reason(s) for the high prevalence of CKD in the elderly, it is clear that as the population ages we can expect to see a large expansion in the number of older individuals who meet current criteria for CKD. For example, in 2000, there were approximately 25 million adults 70 years or older, accounting for 9% of the population. By the year 2050, based on US Census Bureau projections, there will be more than 66 million people over the age of 70 and this group will account for approximately 16% of the overall population [4