Objective In Nicaragua, an epidemic of chronic kidney disease (CKD) with unknown aetiology has been described primarily among young, male sugarcane workers. Our goals were to characterise the type of kidney damage and evaluate the potential role of occupational factors.
Methods Our study population included 284 sugarcane workers, 51 miners, 60 construction workers, and 53 port workers in Western Nicaragua. For sugarcane workers in seven jobs (e.g. cane cutters, pesticide applicators, etc.), blood and urine samples were collected at the beginning and end of the 6-month sugarcane harvest. One round of samples were also collected from workers who were employed in the other three industries (but had never worked in the sugarcane industry). Biomarkers of kidney injury included serum creatinine, urinary albumin, and urinary neutrophil gelatinase-associated lipocalin (NGAL). Linear regression models were used to determine whether biomarkers of kidney injury increased during the harvest and/or varied by job.
Results Biomarkers of kidney injury were significantly different by sugarcane job and estimated glomerular filtration rate (eGFR) declined significantly during the harvest among those engaged in the most strenuous work tasks, while urine albumin remained low in all groups. Compared to factory workers, eGFR was lowest among cane cutters (p = 0.006) and urinary NGAL was highest among cane cutters (p = 0.04). Workers in other industries also had higher than expected prevalence of eGFR <60 mL/min/1.73 m2.
Conclusions Our results provide evidence that the type of kidney damage occurring in sugarcane workers, as well as among workers in other industries, is primarily tubulointerstitial (and not glomerular) in nature. Biomarkers of kidney injury varied by job and were highest among workers engaged in more strenuous physical labour. If acute kidney damage is on the causal pathway to CKD, heat or other work-related exposures may be contributing to this epidemic.