Extreme Heat and Chronic Kidney Disease (CKD)

Almost fifteen years ago, the first reports of an unusual form of chronic kidney disease (CKD) emerged from the lowlands of Central America.(1,2) A tiny band of astute internists practicing in rural clinics in Nicaragua and El Salvador noticed over a period of years an epidemic-scale increase in the prevalence of CKD among the agricultural workers in their communities. The condition was both irreversible and progressive in a region poorly able to support the needs of the growing numbers of people with End-Stage Kidney Disease (ESKD). In the lowland plantations, the hotter regions, slash-and-burn farming of crops like bananas was still practiced, and the use of toxic chemical fertilizers was not regulated tightly—but those factors had not changed for decades. Something else was happening. The same kind of kidney disease was not found among workers at cooler upland plantations in the mountains where crops like coffee and cacao were raised. Since then, this condition has been described among workers in similar conditions in Sri Lanka and southern India and Thailand. Similar kidney disease attributed to chronic heat stress has also been described in steel factory workers in southern India.

Since the initial descriptions, numerous studies have confirmed the existence of this new expression of kidney failure, and many more have been done to characterize it. The steps in the pathophysiology have been described, starting with elevation of core body temperature, leading to renal inflammation, mitochondrial oxidative stress—the usual cellular and molecular suspects, once the focus is fixated internally. There might be some component of direct toxicity from chemical exposure and inhaled particulates from slash-and-burn, but the susceptibility to the latter injuries was enhanced because of the primary heat-induced injury. It has been given a number of different names (CKDu and CKDnt are the most commonly used). You can think of it as a slowly advancing ischemic ATN that becomes chronic and irreversible. The bottom line is that the sine qua non of this entity is prolonged, repetitive exposure to extreme environmental heat. Remediation efforts would seem to be self-evident—decreasing workers’ heat exposure and assuring their hydration, for starters. Simply common sense. There are studies that address the value of such interventions in amelioration of risk and prevention of heat-stress related kidney disease.(3) But academic studies in the renal literature can only address obliquely the wide range of social, economic and even political issues that might mitigate against wholesale remediation policies that could protect workers from this condition. And even if the countries most affected would take it upon themselves to alter their policies to protect these workers, and to suffer whatever economic losses they might sustain from reduced agricultural productivity, the underlying pathogenic factor remains: overexposure to increased ambient temperature—that is, the undeniable trends of rising temperatures globally. This is not going to improve or reverse on its own.

Research continues in Central America, though remedial efforts are difficult to put in place.(4) Thus far, evidence of this condition in the United States is not strong, though surveillance has begun.(5) There have been studies. But our bananas, coffee and cacao—among other favorite foods—are not grown here; for the most part, they are imported from exactly the parts of the world experiencing this malady most acutely. It’s not about the bananas, of course—it’s about the patients who are suffering with this condition and related conditions attributable to climate change.

Spotting a heat-related condition of the lethality of ESKD in faraway places where we can do little to intervene can be frustrating to us as physicians. Our impulse is to act, but what action can we take? One response is to just write it off, erase it from our awareness. Another is to keep it intellectual, protect ourselves from personalizing it. However, if global warming trends continue, and they are projected to do just that, we will not have the luxury of doing nothing for much longer. Where there is this much heat, there will eventually be smoke, and as the old adage goes, where there is smoke, there is fire.

The physician—in particular (I believe) the osteopathic physician—of the 21st century must come to see that the planet is our patient as much as are we dwellers upon it, and as much so as the patients we see in our clinics and offices. Our advocacy for our patients does not stop at the clinic door. Just as we advocate for our patients’ health, we will have to advocate for the planet’s health. In previous issues of ACOInfo, Dr. Badger has referenced the Global Consortium on Climate and Health Education (GCCHE). This is a great place to start—or continue—your education on climate health. Also, check out the Medical Society Consortium on Climate and Health, an organization of medical societies dedicated to education and action. ACOI is the first and only osteopathic organization to be affiliated with the Medical Society Consortium, and I count that as something we should be proud of. Continue your education on these sites. Then make a decision as to where your actions might do the greatest good, where your actions might nudge us toward healing. After all, isn’t that our responsibility as physicians?    

References:

1. Gonzalez, M et al. Nefrologia, 2011.
2. Lopez M et al. Ciencia y Salud, 2011.
3. Venugopal V et al. Sci Total Environ, 2020.
4. Petropoulos ZE et al. J Expo Sci Environ Epidemiol 2023.
5. Smith DJ et al. J Agromedicine, 2022. 

Note: The views expressed in this article are the author’s own and do not necessarily represent the views of ACOI.