Ageing and Kidney Disease
Long-term studies show that after we cross the age of 30 years we lose 10per cent of our kidney function for every decade of life
It is a sad fact of life, but everyone gets old! Not only are we getting older, but more and more of us in the world are getting older. According to the WHO (World Health Organization), elderly are defined as individuals over the age of 65 years. Going by this definition, over 20 per cent of the world would be elderly. But due to greater medical advances, life expectancy is increasing.
According to global demographic projections, the number of elderly people is expected to triple by the year 2050 and they would make up 33 per cent of the world population. By then, the elderly will outnumber children. In India, in the 20th century, the total population increased three-fold but the population of the elderly increased seven-fold.
Having said that, a number of age-related diseases, kidney disease, being one amongst them, is also gaining more importance now. Geriatric medicine in the treatment of diseases in the elderly has also taken on much more relevance today and it is useful to know how the elderly are affected by kidney disease.
What Happens To Our Kidneys As We Age
Before we try to understand the unique characteristics of kidney disease in the elderly, it is useful to know what ageing does to our kidneys. Long-term studies show that after we cross the age of 30 years, we lose 10 per cent of our kidney function for every decade of life. Hence an 80-year-old would have lost half of his original kidney function due to ageing alone1 So, ageing interferes with both the structure as well as the functions of the kidney.
As we grow older, the kidneys reduce in both size and weight from their normal length of nine to eleven centimetre and normal weight of 120 to 180 grams. The number of filtration units (called glomeruli) decrease in number. Usually, there are 1.3 million glomeruli in each kidney. Each of the remaining glomeruli also develops scars, which keep increasing with age.
The absorptive units (called tubules) get gradually atrophic and non-functional. The scaffolding units, where the glomeruli and tubules are embedded, get stiff and non-flexible. These scaffolding units form the backbone of the kidney and are called the interstitium. Finally, the blood vessels supplying the kidneys also get thickened and narrowed putting the kidneys on the brink of blood deprivation and failure due to lack of blood supply.
As if these structural changes were not bad enough, the ageing kidney also undergoes changes that affect its functions as well. Its ability to filter the blood that flows through it, reduces leading to water retention, high blood pressure and toxin overload. It loses ability to retain sodium leading to frequent dehydration. Also, with ageing, the kidney does not excrete potassium properly causing heart blocks. There is decreased production of haemoglobin-producing hormones and vitamin D which leads to anaemia and bone disorders. Finally, ageing leads to the impairment of insulin clearance, causing high insulin levels and episodes of hypoglycaemia or dangerously low blood sugar levels.
To make matters worse, the standard tests to estimate kidney function are erroneous and misleading in the elderly. This makes treatment even more difficult and complicated. Thus, kidney disease in the elderly is getting more and more important and relevant, especially with the Lycoming of age’ of more people due to greater life expectancy, this presents as a ‘growing’ challenge for all concerned.
Cardio Renal Syndrome
Any kind of heart disease can cause kidney disease. In fact, heart diseases are invariably followed by kidney disease and vice versa. It is a well-known fact that heart disease affects the elderly mainly and thus cardiorenal disease is more common amongst them.
Reno Vascular Disease
In the elderly, blood vessels all over the body get narrowed or blocked. This includes the blood vessels of the heart, brain, limbs and intestines. And the kidneys are no exception and damage to their blood supply is called Reno Vascular Disease, which leads to high blood pressure and kidney failure.
Drug-Induced Kidney Disease
The elderly are usually taking a multitude of drugs for various age-related illnesses. Thus, they could be taking painkillers for arthritis, blood pressure medications for high blood pressure, anti-diabetic medicines for diabetes and cardiac drugs for heart disease and so on. This kind of Lpolypharmacyl predisposes them to drug-induced kidney damage.
With ageing, the prostate gland enlarges in size. Since it lies right at the junction of the urinary bladder and the urethra, enlargement leads to obstruction of urinary flow. This causes retention of urine and subsequent urinary infections and backpressure kidney damage.
Ageing and Kidney Disease
These are the commonest causes of kidney damage globally and are typically ‘old age’ diseases.