When Dr. Marvin Gonzalez Quiroz was a medical student in Nicaragua, he noticed something startling. Young men, some in their late teens, were being admitted to the hospital with kidney failure. They didn't have diabetes or high blood pressure. They weren't obese. But their kidneys were failing. Many of them were dying, and no one could figure out why.
"This disease is affecting a young population working in agriculture mostly, but there are other workers who are being affected," Gonzalez Quiroz explained, including construction workers and miners.
This nagging mystery has shaped the course of Gonzalez Quiroz's career. After completing his medical degree, he got a master's degree in epidemiology, then began working as a research assistant studying environmental and occupational pollutants in Nicaragua.
In 2014, he launched The Nicaragua Prospective Community-based Cohort Study. With 1,000 participants he's followed for 10 years, it is the longest and largest cohort of its kind investigating the specific type of chronic kidney disease, known as CKDu, Mesoamerican Nephropathy, and Chronic Interstitial Nephritis in Agricultural Communities. The mission of this research is to investigate the progression and causes of CKDu, which was and still is killing people in lower and middle-income countries by the tens and perhaps hundreds of thousands.
Assistant Professor
Department of Environmental and Occupational Health
Kate Marmion School of Public Health
"The prevalence of CKDu ranges from about 10 to 20% of the population in some communities that are affected by this disease," Gonzalez Quiroz explained, "And in a high-risk area, the prevalence of reduced kidney function among men can reach from 19 to 40% compared with five to 14% among women."
Now, as an assistant professor in the Department of Environmental and Occupational Health at the UT School of Public Health San Antonio, Gonzalez Quiroz's research has expanded to include collaborations on studies in South India and Sri Lanka, where laborers also face high rates of kidney disease with no obvious cause. The South Asian studies use the standardized protocol he developed in Nicaragua.
So what's going on?
"The most likely hypothesis is that repeated episodes of heat stress combined with dehydration in workers doing intense physical labor in a hot environment may lead to a recurrent acute kidney injury, which gradually accumulates and results in chronic kidney disease," according to Gonzalez Quiroz. Other possibilities include exposure to pesticides or agrichemicals, drinking water contaminated with heavy metals like arsenic or lead, overuse of non-steroidal anti-inflammatory medications, poor nutrition, or all of the above.
"We believe that the etiology of the disease could be multifactorial," Gonzalez Quiroz said, "Because there is no single risk factor that can explain the high prevalence of chronic kidney disease in those countries in Central America."
Gonzalez Quiroz is hoping to learn more about how heat stress and other factors impact the kidneys by launching a pilot study this summer in San Antonio. "Our plan is to enroll 20 outdoor workers who are exposed to heat and to follow them for a week using personal wearables to track heart rate, core body temperature, and the physical workload as well." His team will also collect blood and urine samples before and after shifts to measure values associated with kidney health.
"We expect to see that the incidence of acute kidney injury is similar to what we have seen in other countries because San Antonio is very hot," Gonzalez Quiroz said. "The temperature is quite similar to Mesoamerica during the summer."
The pilot study will be small, but could lead to a much larger study in the United States. Gonzalez Quiroz says it's essential to gather new knowledge on this topic now because, as the planet warms, the impacts of heat stress on health will likely be felt far beyond Central America.
"Nobody escapes that," Gonzalez Quiroz said. "So that is our main goal. To generate new knowledge and evidence that can be used for protecting workers in the workplace."
Gonzalez Quiroz has also secured a $30,000 grant from the Medical Research Council in the United Kingdom to support the 10th year of follow-up fieldwork for his ongoing study in Nicaragua.
