Published: May 19, 2016

Global warming will likely exacerbate epidemics of chronic kidney disease seen recently in hot, rural regions of the world, according to a new assessment by an international team of researchers, including two from the University of Colorado Boulder. 

Chronic kidney disease caused by heat stress and dehydration appears to be increasing in communities in the Americas, Southeast Asia, Africa and the Middle East as regional temperatures rise, the authors wrote in an assessment published in the Clinical Journal of the American Society of Nephrology this month. 
Chronic kidney disease, or CKD, means a loss in kidney function, problematic because our kidneys filter waste and excess fluid from blood. 
“Temperature increases add an additional dimension to this health issue,” said Balaji Rajagopalan, a climate change expert, Fellow of the Cooperative Institute for Research in Environmental Sciences at CU-Boulder and professor of engineering.
“In this paper, we find that in some places—mostly tropical countries where you have weak public health systems—temperatures are going up and people in farm sectors are vulnerable,” Rajagopalan said. 
People with CKD are more vulnerable to some types of environmental toxins as well as many other health challenges, including diabetes and even kidney failure. 
Co-author Richard Johnson, a kidney disease expert and professor of medicine at the University of Colorado Anschutz Medical Campus, said CKD associated with heat stress and dehydration may represent “one of the first epidemics due to global warming."
Dr. Johnson published work last year reporting that CKD related to heat stress and dehydration in Central America likely killed more than 20,000 people between 2002 and 2015, most of them sugar cane workers who spent long hours in hot conditions.
For the new, global analysis, Rajagopalan and Henry Diaz, a CIRES and NOAA research scientist, helped their medical colleagues assess the relationship between disease patterns and temperature trends in many parts of the world. 
People at risk of heat-related CKD are often from “impoverished and neglected” rural communities, the authors noted, so the research team did not always have access to medical surveillance data.
The new study relied on reports from a diversity of sources, from published papers to phone conversations with health experts in various parts of the world.
In some places, the scientists found higher levels of CKD in rapidly warming areas (e.g., the Pacific coasts of Nicaragua, El Salvador and Costa Rica) compared to nearby areas with similar agricultural intensity but cooler temperatures.
The reports often contained other clues linking the disease to heat stress and dehydration: Male agricultural workers might have significantly higher disease rates, for example, than women and children in their communities. 
The researchers recommended that governments and scientists begin better documenting the presence of chronic kidney disease epidemics and work to develop interventions to improve outdoor worker hydration. 
With climate change expected to worsen heat wave frequency and intensity in many parts of the world in the future, the interdisciplinary team is continuing to work together, Rajagopalan said. “Our research communities are very different, so this kind of collaborative approach can offer rich insight as we think outside different boxes.” 
The American Society of Nephrology, La Isla Foundation and the University of Colorado Anschutz Medical Campus contributed to this report.
CIRES is a partnership of NOAA and the University of Colorado Boulder
Balaji Rajagopalan, CU-Boulder and CIRES, 303-492-5968
Katy Human, CIRES communications, 303-735-0196 
David Kelly, University of Colorado Anschutz Medical Campus communications, 303-724-1525
Kevin Alfonso Alas Enriquez

Kevin Alfonso Alas Enriquez, 24, used to cut sugarcane but now carries shade tents and water into a sugarcane field as part of an intervention designed to improve working conditions, minimize the negative impact of heat stress, and measure health outcomes. Photo: Tom Laffay/La Isla Foundation