Blog entry by Meguid El Nahas

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by Meguid El Nahas - Friday, 12 December 2014, 8:39 AM
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Am J Kidney Dis. 2014 Nov 5. pii: S0272-6386(14)01363-8. doi: 10.1053/j.ajkd.2014.09.023. [Epub ahead of print]

The Future Burden of CKD in the United States: A Simulation Model for the CDC CKD Initiative.

Abstract

BACKGROUND:Awareness of chronic kidney disease (CKD), defined by kidney damage or reduced glomerular filtration rate, remains low in the United States, and few estimates of its future burden exist.

STUDY DESIGN:We used the CKD Health Policy Model to simulate the residual lifetime incidence of CKD and project the prevalence of CKD in 2020 and 2030. The simulation sample was based on nationally representative data from the 1999 to 2010 National Health and Nutrition Examination Surveys.

SETTING & POPULATION:Current US population.

MODEL, PERSPECTIVE, & TIMELINE:Simulation model following up individuals from current age through death or age 90 years.

OUTCOMES:Residual lifetime incidence represents the projected percentage of persons who will develop new CKD during their lifetimes. Future prevalence is projected for 2020 and 2030.

MEASUREMENTS:Development and progression of CKD are based on annual decrements in estimated glomerular filtration rates that depend on age and risk factors.

RESULTS:For US adults aged 30 to 49, 50 to 64, and 65 years or older with no CKD at baseline, the residual lifetime incidences of CKD are 54%, 52%, and 42%, respectively. The prevalence of CKD in adults 30 years or older is projected to increase from 13.2% currently to 14.4% in 2020 and 16.7% in 2030.

LIMITATIONS:Due to limited data, our simulation model estimates are based on assumptions about annual decrements in estimated glomerular filtration rates.

CONCLUSIONS:

For an individual, lifetime risk of CKD is high, with more than half the US adults aged 30 to 64 years likely to develop CKD. Knowing the lifetime incidence of CKD may raise individuals' awareness and encourage them to take steps to prevent CKD. From a national burden perspective, we estimate that the population prevalence of CKD will increase in coming decades, suggesting that development of interventions to slow CKD onset and progression should be considered.

 

COMMENTS:
We are mystified and deeply troubled by what appears to be a "fear mongering" simulation of the life-time risk of developing what is unreasonably called "CKD" recently published on-line in the AJKD (Hoerger, TJ; Simpson, SA; Yarnoff, BO; Pavkov, ME; Ríos Burrows, N; Saydah, SH; Williams, DE; Zhuo, X. The Future Burden of CKD in the United States: A Simulation Model for the CDC CKD Initiative Am. J. Kidney Dis., 2014- on-line- December 6, 2014). Both the authors and the reviewers of this paper clearly accept the notion that as humans age the GFR falls. They must also realize that the application of a fixed, absolute and arbitrary threshold of GFR as a definition for "CKD", without reference to other manifestations of kidney disease (such as overt albuminuria) will always and predictably lead to an increase in "CKD" as one grows older and GFR falls. Thus, it is expected and unsurprising that as populations and individuals age the incidence and prevalence of "CKD", defined in this fashion, will rise in a commensurate fashion. Does this mean that life expectancy is curtailed to any significant extent by this age-related" and artificially-created "pseudo-CKD"?  No!  Does this mean that the new label imposes any special burden on the person so labeled?  No!, except for the anxiety and fear that it engenders and the resulting “medicalization” of ageing and associated events such as falling GFR.

This publication, by suggesting that individuals can all look forward to a 1:2 chance of developing "CKD" over our lifetimes and that our societies can anticipate a secular increase in the prevalence of "CKD",  carries with it a deep responsibility to explain the origins of these phenomena to the reader in a clear and unequivocal way.  After all, the lifetime chance of dying is 1:1 and we all intrinsically understand what this means; namely, that death is inevitable, the process is biological and begins at the time of birth. Similarly, the decline GFR, in those who survive over 65 years of age, is also a biological process that will affect an increasing percentage of the ageing population. In addition, no cogent explanations are offered for the huge gaps in prevalence of “CKD” between Category 2 and Category 3A and Category 3B—if the CKD Categories represent some kind of naturall progression why do these discrepancies occur?

It is disappointing that the extremely worthwhile aspects of the CKD concept are being twisted in such an unhelpful way that obfuscates the real  risks of meaningful (treatable) CKD.  An obvious solution would be to age-calibrate the thresholds of eGFR used for defining CKD (in the absence of other disease defining features), in the first place.  One might anticipate that if this were done the frightening characteristics of the simulation would take on a more subtle, less dramatic hue. Only then will life-time risks of CKD assume meaningful significance to individuals, populations and societies.

 Richard J. Glassock

Meguid El Nahas

Pierre Delanaye 

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