Background: There is an epidemic of chronic kidney disease (CKD) of unknown etiology in Central American workers. Objectives: To investigate changes and job-specific differences in kidney function over a 6-month sugarcane harvest season, explore the potential role of hydration, and measure proteinuria. Methods: We recruited 284 Nicaraguan sugarcane workers performing seven distinct tasks. We measured urine albumin and serum creatinine and estimated glomerular filtration rate (eGFR). Results: eGFR varied by job and decreased during the harvest in seed cutters (28.6 ml/min/1.73 m 2 ), irrigators (27.4 ml/min/1.73 m 2 ), and cane cutters (25.0 ml/min/1.73 m 2 ), as compared to factory workers. The number of years employed at the company was negatively associated with eGFR. Fewer than 5% of workers had albumin-to-creatinine ratio (ACR) .30 mg/g. Conclusions:The decline in kidney function during the harvest and the differences by job category and employment duration provide evidence that one or more risk factors of CKD are occupational.

Background In Central America, an epidemic of chronic kidney disease of unknown etiology disproportionately affects young, male agricultural workers. Study Design Longitudinal cohort study. Setting & Participants 284 sugarcane workers in seven jobs were recruited from one company in northwestern Nicaragua. Blood and urine samples were collected before and near the end of the six-month harvest season. Predictors Job category (cane cutter, seeder, seed cutter, agrichemical applicator, irrigator, driver, factory worker); self-reported water and electrolyte solution intake. Outcomes & Measurements Change in urinary kidney injury biomarkers normalized to urine creatinine, including neutrophil gelatinase-associated lipocalin (NGAL), interleukin 18 (IL-18), N-acetyl-β-d-glucosaminidase (NAG), and albumin; serum creatinine–based estimated glomerular filtration rate (eGFR). Results Mean eGFR was 113 mL/min/1.73 m2 and less than 5% of workers had albuminuria, field workers had increases in NGAL and IL-18 that were 1.49 (95% CI, 1.06-2.09) and 1.61 (95% CI, 1.12-2.31) times as high, respectively, as in non-field workers. Cane cutters and irrigators had the greatest increase in NGAL during the harvest, while cane cutters and seeders had the greatest increase in IL-18. Consumption of electrolyte solution was associated with lower mean NGAL and NAG among cane cutters and lower mean IL-18 and NAG among seed cutters; however, there was no overall effect of hydration among all workers. On average, workers with the largest increases in NGAL and NAG during the harvest had declines in eGFR of 4.6 (95% CI, −8.2 to −1.0) and 3.1 (95% CI, −6.7 to 0.6) mL/min/1.73 m2, respectively. Limitations Surrogate exposure measure, loss-to-follow-up. Conclusions Results are consistent with the hypothesis that occupational heat stress and volume depletion may be associated with development of kidney disease, and future studies should directly measure these occupational factors. The presence of urine tubular injury markers supports a tubulointerstitial disease that could occur with repeated tubular injury.

Leptospira seroprevalence varied by job category. There was some indication that seropositivity was associated with elevated biomarker levels, but results were inconsistent. Additional studies may help establish whether Leptospira infection plays any role in MeN among Central American workers.

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