Kidney function changes in sugarcane workers in the south coast, KwaZulu Natal, South Africa
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Date
2019
Authors
Magombo, Mollen
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Abstract
Introduction: Epidemic chronic kidney disease of unknown cause (CKDu) occurs among sugarcane workers, notably cane cutters doing heavy manual work in hot tropical environments in Mesoamerica. Repetitive dehydration consequent on strenuous work in heat is postulated to be the cause. A Nicaraguan cohort study showed remarkable kidney function decreases across six weeks of the cane-cutting season consistent with the dehydration hypothesis. This Nicaraguan study was replicated on a sugar plantation in South Africa about 3 400 kms from the equator and cooler than previous study locations to examine whether less extreme ambient conditions resulted in reduced kidney stress.
Methods: 37 cane cutters and 36 referents of similar socio-economic status but doing less strenuous work on the same plantation had their blood and urine samples assessed for biomarkers of kidney function with the aim of assessing changes in kidney function and hydration across ten weeks of cane cutting. The cutters were examined on Day 1 (start of cutting season), Day 10 and Week 10 of the cutting season, pre- and post-shift. The reference group was examined only on Day 1 and Week 10. CKD-EPI equation was used to calculate the estimated glomerular filtration rate (eGFR) base on creatinine.
Results: Among cane cutters, mean pre-shift serum creatinine increased by 7% and 14% on Day 1 and week 10 respectively; and eGFR decreased across shift by 3% and 5% respectively. These changes were consistent with kidney stress over the shift. Whereas no change was observed across the season in eGFR. Pre-shift Cystatin C increased by 15%, NGAL decreased by 3.6%, serum creatinine decreased by 1% and eGFR increased by 1.4% across the 10 weeks of cutting.
Conclusion: Overall, our study found evidence of effects on kidney function after 10 weeks of cane cutting, but milder than those reported in hotter and lower altitude settings. Our findings are of concern as it is postulated that minor effects when repeated frequently over years may result in significant renal injury.
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A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Medicine (Community Health) in the field of Public Health Medicine
October 2019