Chronic, severe dehydration linked to working in hot, humid climates for long hours may be accelerating rates of chronic kidney disease (CKD). Research published in the Clinical Journal of the American Society of Nephrology (CJASN) suggests that a condition called heat stress nephropathy may represent a disease of neglected populations, but one that may emerge as a major cause of poor kidney health as the climate continues to change (Glaser J, et al. Clin J Am Soc Nephrol. doi:10.2215/CJN.13841215 [published online May 5, 2016]).
Over the next century, climate change and resulting water shortages are likely to affect a wide variety of health issues related to dehydration and heat stress—with risks increasing for cognitive dysfunction, malnutrition, waterborne infectious diseases, CKD, and other conditions. Some health situations, such as a great geographic spread of tropical and infectious diseases, may be more noticeable than gradual changes such as incremental increases in pollen counts that could lead to longer allergy seasons and worse asthma cases. In this latest CJASN research, investigators found that CKD that is not associated with traditional risk factors (CKDu) also appears to be increasing in rural hot communities as worldwide temperature progressively rises.
The researchers believe the risk for heat stress nephropathy—or CKD consistent with heat stress—has increased owing to global warming and an increase in heat waves, and it is having a disproportionate impact on vulnerable populations, such as agricultural workers.
“So far, the profile for impacted communities seems to be extreme heat and heavy labor. As you leave these extremely hot areas, there are far fewer cases recorded to date even though some of the other proposed risk factors remain relatively unchanged,” said lead author Jason Glaser, of La Isla Foundation, in Nicaragua and the US. Decreasing precipitation exacerbates this epidemic by reducing the water supply and water quality as temperatures climb.
“We were able to connect increased rates of chronic kidney disease in different areas to an underlying mechanism—heat stress and dehydration—and to climate,” said senior author Richard Johnson, MD, of the University of Colorado School of Medicine. “A new type of kidney disease, occurring throughout the world in hot areas, is linked with temperature and climate and may be one of the first epidemics due to global warming.”
Mechanistically, dehydration may inhibit an individual’s ability to excrete toxins as effectively as those who are well hydrated, leading to higher concentrations in the blood and kidney. Dehydration also results in the kidney concentrating the urine. While this is a healthy process that is normally protective in the acute setting, repeated dehydration appears to carry a cost to the kidney, according to Johnson. “Specifically, recurrent dehydration can lead to chronic elevations in vasopressin that may induce kidney damage,” he said. “It can also activate processes that lead to fructose generation in the kidney that can cause local oxidative stress. High concentrations of uric acid can also precipitate in the concentrated urine and may exacerbate injury. These processes may be amplified by rehydrating with drinks high in sugar or high fructose corn syrup.”
Earlier studies by the investigators in Nicaragua and El Salvador revealed a remarkable decrease of kidney function in male sugarcane cutters after high-intensity harvesting in hot conditions (García-Trabanino R, et al. Environ Res 2015; 142:746–755; Wesseling C, et al. Environ Res 2016; 147:125–132). Other studies have uncovered similar hotspots in other parts of Central America, as well as in South Asia, North and South America, Africa, and the Middle East.
“I don’t think this disease is new—I think it has been with us for some time, and is more recognized due to increasing surveillance but also because the factors that put people at risk are exacerbated by extreme demands at the workplace to meet production needs,” said Glaser. “The result is over 40,000 dead in the last 10 years in Mesoamerica and Sri Lanka alone. Of course, we think that due to surveillance being so inadequate for these at-risk populations, the disease is much more widespread.”
To address the problem, interventions—such as those proposed in La Isla’s and Solidaridad’s Worker Health and Efficiency (WE) Program (www.weprogram.org)—are needed to improve worksite conditions and ensure adequate hydration. In addition, governments and scientists should work together to conduct epidemiological and clinical studies to document the presence of these epidemics and their magnitude. To this end, the World Health Organization, in collaboration with the Sri Lankan government, called together approximately 45 global experts from various organizations, institutions, and disciplines in late April. Also, Johnson is working with Glaser and others on a simple and practical protocol to estimate distributions of kidney function in rural communities globally. The Disadvantaged populations estimated glomerular filtration rate (eGFR) epidemiology study (DEGREE) will provide key information to inform hypotheses and to guide further research into the sources of CKDu.