Over the last few decades, an increasing number of cases of chronic kidney disease have emerged among agricultural workers, particularly in Central America. The disease is characterised by a gradual loss of renal function and is not associated with diabetes or hypertension, the main causes of traditional chronic kidney disease. It is strongly associated with working and living in a hot environment, but the cause is not yet known. It could be a toxin, an infectious agent, a heat-associated injury, strenuous work, or a combination of multiple factors.

Cristina O’Callaghan and an international group of researchers set out to assess whether chronic kidney disease of unknown origin (CDKu) is also present in India and to identify risk factors. They used data on 12,500 people from three population studies in urban and rural areas of northern and southern India. The participants had previously answered questionnaires on dietary habits, alcohol consumption, education level and other sociodemographic characteristics. Their body mass index and blood pressure were also measured, as well as biomarkers of renal function.

The team found that the average disease prevalence was 1.6% but that it varied greatly between regions. It was highest in rural areas of southern India, where it reached 4.8%. The major risk factors were being of working age (under 60), living in a rural area, alcohol consumption and lower education level. “These risk factors are similar to those previously described in Central America and Sri Lanka, and could be linked to agrochemical exposures,” says O’Callaghan. The findings have important implications for global health, since they indicate that CDKu may have a greater public health burden than previously recognised.