GFR decline and prior dysuria among Nicaraguan sugarcane workers

Abstract

BACKGROUND AND AIM: Nicaraguan sugarcane workers have an elevated prevalence of chronic kidney disease of unknown origin, referred to as Mesoamerican Nephropathy (MeN). Work in the sugarcane industry involves exposure to climatic heat and strenuous physical labor, suspected contributors to the development of MeN. These same factors may increase the risk of dysuria, thought due to crystalluria, which in other disease states has been associated with acute kidney injury. In a longitudinal study of sugarcane workers, we examined whether experiencing dysuria was associated with subsequent reduced kidney function. METHODS: At a sugarcane company in Nicaragua, we abstracted employment and medical records for 190 male workers (1997–2010). Dates worked, jobs held, and medical data were collected. Estimated glomerular filtration rate (eGFR) was categorized as a binary outcome, first analyzed as 90 (includes mild and moderate eGFR reduction) and then analyzed as 60 (focused on moderate eGFR reduction) mL/min/1.73m2. To examine the association between prior dysuria diagnosis (ever/never) and reduced eGFR, logistic regression based on generalized estimating equations for repeated events was used to estimate the odds ratio (OR) and the 95% confidence interval (CI), controlling for age, cumulative harvest seasons worked, proportion seasons worked as cane cutter, and period of the harvest season. RESULTS:A total of 1,676 eGFR measurements were available for 190 workers. There were 134 workers with at least one dysuria diagnosis, and 72% of eGFR measures were preceded by a dysuria diagnosis. eGFR 90 [adjusted OR=2.27 (95% CI 1.40, 3,67)] and eGFR 60 [adjusted OR=3.87 (95% CI 1.81, 8.25)] were both associated with having a prior dysuria episode. CONCLUSIONS:Experiencing dysuria was associated with an increased risk of reduced eGFR. These findings suggest that crystalluria may contribute to subsequent transient changes in kidney function, though more research is warranted. KEYWORDS: Temperature, Occupational Epidemiology, Cardiovascular diseases, International collaboration, Climate