Am I sick or just O.L.D?
February 21, 2018
Ageing should not be viewed synonymously with disease
When I last visited my 89-year old grandmother, she showed me the latest additions to her webster pack, including a new blood pressure-lowering medication. She informed me that this had been started since her last visit to hospital, where she had been “diagnosed” with Stage 3 chronic kidney disease (CKD) following a routine blood test.
Kidney function is assessed by measuring creatinine levels (a waste product in the blood), which is used to calculate the estimated glomerular filtration rate (eGFR). The eGFR provides an indication of how well the kidneys are working. Stage 3 CKD is diagnosed when eGFR is below 60ml/min/1.73^2 for at least three months. This level represents half the level of expected kidney function of a healthy young adult. This threshold for diagnosis is somewhat arbitrary and has attracted some controversy since it is not adjusted for age or sex.
A 2013 analysis article in the BMJ by Ray Moynihan and colleagues argued that this definition invites large potential for overdiagnosis of chronic kidney disease. Under this definition, around half of people over the age of 70 could be labelled as having chronic kidney disease.
Kidney function normally trends down with age, and the vast majority of those diagnosed with CKD (particularly stage 3 CKD) have eGFRs that fall within the expected normal range for their age. Many of them don’t even show signs of kidney damage such as albuminuria (loss of protein in the urine), so the only factor contributing to a CKD diagnosis is simply one’s age.
The premise of classifying CKD into its various stages based on eGFR was to provide some degree of consensus amongst clinicians. It also aimed to prevent progression to end stage renal failure or cardiovascular disease by detecting early signs of kidney decline. In doing so, this diagnostic threshold has incidentally detected a lot of people who have normal and healthy, albeit ageing kidneys. Studies have shown that approximately a third of people over the age of 65 meet the current definition of CKD but only 0.1% of those diagnosed progress to end-stage renal disease.
The conversation around overdiagnosis of CKD has been ongoing for the past decade. This started to make me wonder about other diseases that are diagnosed on the basis of arbitrary thresholds not adjusted for age, that may instead represent normal ageing.
It is already accepted that most, if not all organs decline with age at varying rates depending on genetic and environmental factors. However, it is important to distinguish normal ageing from pathological ageing – that is, when normal age-related decline is altered by disease – so that medical attention is paid to the people who genuinely require it.
Ageing should not be viewed synonymously with disease. Labelling healthy people as ‘sick’ not only has psychological and economic implications, it also starts a cascade of unnecessary treatment. As it stands, the evidence for treating risk factors such as osteoporosis and diabetes in the elderly is lacking, though clinicians generally advise to treat the patient and not just his or her numbers.
It is becoming less feasible for elderly people to age comfortably without becoming a patient. Routine screening tests performed by GPs results in abnormal test findings, where “normal” is poorly established in this age group. In addition to eGFR, this issue has been reported for glucose tolerance tests, blood pressure, and bone mineral density measurements.
Calculating the normal rate of organ function decline will assist with estimating the normal range of organ function for ageing people. It may help detect the point at which various organs start to decline. Most importantly, clinicians will be able to reassure patients that their test results are completely normal in the context of their age.
Author: Elizabeth Thomas is a final year medical student from Bond University who is undertaking a research elective with the CEBM.
Acknowledgements: Many thanks to Dr. Kamal Mahtani and Dr. David Nunan for their helpful comments.
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