Elderly patients with glomerular diseases and IgA nephropathy

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Ageing is an enormous challenge of the 21st century. According to 2015 UN reports,1 the percentage of the world population aged ≥60 years was estimated to have reached 12%, a growing rate of 3.26% per year. The growing ageing population is a consequence of longer life expectancies combined with diminishing birth rate. At the beginning of the 20th century, the average life expectancy was 40–45 years. In a span of a little over 100 years, we have doubled our life expectancy to about 80 years. The doubling can be attributed to many factors, including rise in the nation building, use of electricity, provision of a social safety net and advances in technology, including social media. Other major contributors, however, are the advances in medicine and medical science, including the invention of vaccination, antiseptics and antimicrobials, recognition and correction of nutritional defects and treatment of major organ diseases. Remarkably, as early as 1929, Warren Thompson (1887–1973), an American demographer, predicted that with the progression of society, death and birth rates would decrease, resulting in population ageing. Indeed, the 2009 Census showed that many countries, including the United States, China and Japan, had progressed to a birth rate lower than the death rate. Such a shift in the age distribution has had a visible impact on the economy in many regions of the world. In the United States, three workers supported one retiree in 2009, a sharp reduction from a ratio of 16.5: 1 in 1950 (https://www.ssa.gov), a trend that is projected to continue. Given ~90% of healthcare costs fall within the last 2 years of life, the implication of population ageing on the global socio‐economy cannot be underestimated.
Ageing is associated with a progressive decline in kidney function. Studies have shown that 30% of glomeruli become sclerotic in apparently healthy individuals by age 80. Renal inulin clearance drops by half from 120 mL/min per 1.73 m2 in ages 20s down to 65 mL/min per 1.73 m2 in ages >80 years.3 In the United States, a majority of glomerular diseases in the elderly are secondary to chronic conditions, such as hypertension, diabetes and glomerular ischaemia from diffuse atherosclerotic vascular disease. Primary glomerular diseases have been relatively fewer. However, in patients who undergo kidney biopsy, due to variations in biopsy indication, local biopsy policy and practice style among institutions, the most common glomerular diseases in the elderly, based on the kidney biopsy, have been crescentic glomerulonephritis (GN) associated with ANCA‐mediated vasculitis.4 Similarly, in Europe, the top few kidney diseases from biopsy are crescentic GN, chronic GN, membranous nephropathy (MN) and focal segmental glomerulosclerosis (FSGS).6
The kidney disease spectrum in the elderly based on the kidney biopsy varies between Europe/United States and Asia. A recent large single‐centre study in China showed that about 3% (n = 851) of all biopsies (n = 29 425) in the years 2003–2012 were from patients ≥65 years of age.10 The top four most common biopsy diagnoses were membranous nephropathy (28.8%), diabetic nephropathy (9.8%), IgA nephropathy (9.6%) and vasculitis‐associated crescentic GN (6.8%). Similar results were shown in other studies in China, Korea and Japan.11 The difference in the disease spectrum between the Western and Eastern countries could be due to a true difference in disease distribution and/or due to a variation in the indications and local institutional policies for kidney biopsy. Notably, consistent and common findings across geographical and ethnic differences are, as summarized in a recent paper,15 as follows: (i) MN is the most common biopsy diagnosis if indication for the biopsy is nephrotic syndrome and (ii) crescentic GN associated with ANCA‐mediated vasculitis is the most common diagnosis if the indication is acute kidney injury (AKI).
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