Chronic Kidney Disease in India--a Hidden Epidemic‪.‬

There is an epidemiological transition taking place in India, with the decline in communicable diseases and a growing burden of chronic disease. In a recent review, Reddy and others noted that 53 per cent of deaths in India in 2005 were due to chronic disease (1). The principal named categories of chronic disease in their report were cardiovascular disease, cancer, chronic respiratory disease and diabetes. Notably, chronic kidney disease (CKD) was not a category on its own merits but most likely included under the 'other' category. The World Health Organization laid down certain criteria for a major non-communicable disease (NCD), namely, (i) being a major cause of morbidity and mortality, (ii) being amenable to prevention by community based strategies, and (iii) sharing common risk factors with other NCDs (2). Though CKD meets these criteria, it does not find a place in this category. There is no reason to suspect that the global epidemic of CKD does not have its counterpart in India and epidemiologic indicators suggest that it is likely to be sizeable. India has been described as the diabetes capital of the world, every fifth diabetic in the word being Indian (3). Hypertension is not far behind--the CURES cohort in Chennai showed that every fifth individual was hypertensive (4). The increasing prevalence of diabetes, hypertension and associated risk factors such as obesity, hypercholesterolaemia and the metabolic syndrome underscores the potential for sustained and explosive growth of this epidemic. The epidemiology of CKD in India is very different from the West. Patients are roughly two decades younger, and a substantial proportion present with small kidneys, so the aetiology of CKD is unclear (5). The contribution of less well understood risk factors toward these epidemiologic differences is unknown--low birth weight and relationship to diminished nephron number (6), variations in Th1/Th2 regulatory lymphocyte balance and relationship to glomerulonephritis as postulated by the 'Hygiene hypothesis' (7) and the so called 'Asian Indian Phenotype' or 'Thrifty Phenotype' of truncal/visceral obesity and insulin resistance (8), have been poorly studied in this context. What then is the burden of CKD in India? Recent publications have dealt with mainly single centre reports or regional population based estimates and the definition of CKD has differed. In the absence of nationwide reporting systems or registries, the true incidence and prevalence is difficult to determine. Observational and anecdotal data suggest that the normal ranges of glomerular filtration rate (GFR) may be lower in the predominantly vegetarian, less muscular Indian subjects with different creatinine generation rates, compared to their western counterparts although this issue needs more rigorous study (9,10). In the last decade, there has been a major evolution in the definition and classification of CKD that is based upon estimated GFR (11). Application of these definitions would impact identification of disease. Therefore issues of global implementation will need to be resolved. Mani (12), working in Chennai, South India, estimated a prevalence of chronic renal failure of 0.16 per cent in the community in 2003; applying the Modification in Diet in Renal Disease (MDRD) equation for GFR estimation in 2005, 0.86 per cent were found to have a GFR 80ml/min/1.73 [m.sup.2] (13). Agarwal and co-workers 14 arrived at an estimate of 0.78 per cent for CKD, in a community-based sample in New Delhi defined by an elevated serum creatinine 1.8 mg/dl. Estimates for the United States (US) population extrapolated from the National Health and Nutrition Examination Survey (NHANES III) data place the prevalence of CKD stages 4 and 5 (severe decrease in GFR) and CKD stage 3 (moderate decrease in GFR) at 0.4 per cent (11). However, such direct comparisons with Western populations are not valid, since the equivalent GFR for a serum creatinine of 1.8 mg/dl in Indians may place the i