Study shows role of heat stress, volume depletion on kidney failure epidemic among Central American agricultural workers

Heat stress and volume depletion seem to play a role in the epidemic of kidney failure among Central American agricultural workers, according to new research published in the National Kidney Foundation's American Journal of Kidney Diseases.

In Nicaragua and El Salvador, age-adjusted mortality rates from kidney disease are among the highest in the world. The prevalence of kidney disease (defined as eGFR<60 mL/min/1.73m2) in affected communities is 12%-18% in the general population and 14%-26% in men, with age-specific rates among younger men up to 15 times higher than in the United States.

Researchers from the Boston University School of Public Health followed 284 sugarcane workers in seven different jobs from one company in northwestern Nicaragua. . Blood and urine samples were collected from participants before and near the end of the six-month harvest season. Those workers who had the most labor-intensive jobs, cane cutters, had increased urinary neutrophil gelatinase-associated lipocalin (NGAL) and interleukin 18 (IL-18), both biomarkers of kidney injury.

“These individuals have the most physically strenuous jobs in a high-heat setting,” said Rebecca Laws, PhD, a Postdoctoral Associate at Boston University School of Public Health and lead author on the study. “They are also being paid by the amount they cut. It’s a system that can increase physical strain.”

While self-reported hydration didn’t seem to offer any protective benefit to sugarcane workers overall, when stratified by job, researchers observed a protective effect of consuming an electrolyte solution among cane cutters and seed cutters. This indicates there are ways to prevent kidney injury among laborers in high-heat settings.

“At this point we don’t know for certain that heat stress and volume depletion are causal, but we can say that electrolyte supplementation appears to reduce risks of kidney damage in occupations that expose workers to heat stress and volume depletion,” said Dr. Laws.

The authors note there are some limitations to this study, as they didn’t directly measure heat or exposure to chemicals. Job category was used a surrogate for exposure. There is also the possibility of environmental and genetic factors at play. These are all avenues of inquiry that will be studied by Dr. Laws and her team in the future.

“We’re planning a longitudinal study in Nicaragua and El Salvador in sugarcane and other industries to further investigate kidney disease in this region,” Dr. Laws said. “We are also doing a cross sectional study in adolescents and children to find other potential sources of kidney damage in this population.” -by Rebecca Zumoff