For patients with end-stage renal disease (ESRD), extreme heat events (EHEs) are associated with increased risk of hospital admission and mortality, according to a study published online Aug. 9 in JAMA Network Open.
Richard V. Remigio, M.Phil., from the University of Maryland School of Public Health in College Park, and colleagues examined the correlation between EHEs and the risk of hospital admission or mortality among patients with ESRD.
Data were included for 7,445 patients with ESRD, among whom 2,953 deaths and 44,941 hospital admissions were recorded.
The researchers found that among patients with ESRD, EHEs correlated with elevated risk of same-day hospital admission and mortality (rate ratios, 1.27 [95 percent confidence interval (CI), 1.13 to 1.43] and 1.31 [95 percent CI, 1.01 to 1.70], respectively).
Some heterogeneity was seen in risk, with significantly increased risk for mortality associated with cumulative exposures to EHEs among patients in Boston, but not among those in Philadelphia.
Similar increases in risk were seen for non-Hispanic black and non-Hispanic white patients, but the findings were less clear for Hispanic and Asian patients.
“With the projected increases in frequency, duration, and intensity of extreme weather events, future ESRD management guideline[s] need to incorporate EHEs as part of the adaptation measures to minimize morbidity and mortality among patients with ESRD in a changing climate,” the authors write.
Several authors disclosed financial ties to the pharmaceutical and medical technology industries.
One of the pressing challenges facing the world is the increasing impact of climate change and water shortage (driven by both climate change and population expansion) on human health and productivity.
Global warming has resulted in an overall increase of about 0.8°C during the last century, and is estimated to be responsible for 75% of the extreme heat events (1–4).
Heat waves typically refer to sustained temperatures of >40°C, or temperature increases of >5–6°C over the normal maximum temperature of the region, or any time temperatures reach >45°C (5–7).
One of the most intuitive effects of heat waves on human health is heat stroke and death. During the summer of 2015, for example, the heat index – which takes into account both air temperature and humidity – toppled world records at 74°C (165°F) in Iran.
A heat wave in Pakistan resulted in 40,000 cases of heat stroke, and another heat wave in Andhra Pradesh took 1400 lives in 1 month (8–10).
Conditions will worsen, with predictions of a rise of 3–4°C in mean temperature by the end of the century (11), which could result in intermittent temperatures incompatible with outside living in some of the hottest areas of the world, such as the Middle East (12).
The rise in temperature is paralleled by an increasing shortage of water, with the percentage of the world population suffering from moderate water shortage (defined as 1.0–1.7 m3 water/person per year) skyrocketing from 5% in 1800 to 50% in 2005, and with 10% of the world population currently suffering from extreme (<0.5 m3 water/person per year) water shortage (13).
While increased risk for heat stroke is an obvious manifestation of global warming, climate change affects health in many other direct and indirect ways (14,15).
Dehydration secondary to heat stress (relative water loss with development of hyperosmolarity) is associated with cognitive dysfunction, hypotension, and AKI (16).
Drought can reduce crop yields, which can lead to starvation, malnutrition, and act as a threat multiplier to poverty and violence, especially in regions of the world with poor governance; likewise, extreme heat waves kill heat-sensitive cereals such as wheat and rice (17–19).
Alterations in water supply, with variations in precipitation, can lead to emergence of water-borne and vector-borne infectious diseases (20,21).
Drying up of wells can lead to increased concentration of heavy metals and/or toxins. Furthermore, subjects who are chronically dehydrated may not excrete toxins as effectively as those who are well hydrated, leading to higher concentrations of toxins in the serum and kidney.
In addition, chronic dehydration and hyperosmolarity have also been linked with increased risk for obesity, diabetes, and metabolic syndrome (22,23).
Thus, a wide variety of health issues are likely to result from climate change over the next century, emphasizing the importance for educating physicians, industry, policy makers, and the public.
Recently, an epidemic of CKD of unknown etiology has been recognized in Central America (Mesoamerican nephropathy), which has been linked with recurrent dehydration and heat stress (24–26).
We and others have previously suggested, based on both experimental and epidemiologic studies, that this disease may be a type of heat stress nephropathy (HSN) and could be an example of a disease that is accelerated by global warming (27,28).
If true, one might hypothesize that similar epidemics should be occurring among those working manually in other hot environments.
Unfortunately, the subjects at risk are often from impoverished and neglected populations where medical care is poor, renal biopsies are rarely performed, and diagnosis is rarely confirmed. Nevertheless, there are reports of CKD of unknown etiology emerging in other regions of the world where individuals are performing strenuous manual labor under very hot conditions (29–31).
Here, we provide a brief summary of these epidemics, and evaluate the relationship to heat stress, local environmental changes (global warming and progressive water shortages), and dietary changes (increased sugar intake).
Although surveillance data are limited, the populations identified as most at risk are heavy laborers with a high workload, limited access to potable water, and otherwise extreme working conditions (32–34). We propose that HSN may be a major cause of CKD, representing an overlooked disease in neglected populations in hot communities. We suggest it may also emerge as a cause of CKD in any population where subjects are exposed to heat stress.
Limitations
While the epidemics of CKD in Central America, India, and Sri Lanka are associated with recurrent heat stress and dehydration, more studies need to be performed to address if this mechanism is causal and whether similar processes are occurring at other sites (Table 1).
Based on temperature patterns, we predict that similar epidemics of CKD from HSN may be ongoing and potentially discoverable in the hotter regions of Africa and the Middle East.
However, it is important to recognize that toxicity from agrochemicals, heavy metals, and nonsteroidal anti-inflammatory drugs remain potential contributing factors.
It is also important to recognize that reports of CKD of unknown etiology do not in themselves support the presence of HSN, but rather require epidemiologic studies investigating the role of heat stress and recurrent dehydration as risk factors.
It also remains possible that some of the “epidemics” may represent improved awareness and diagnosis rather than a new epidemic.
Nevertheless, temperature maximums are increasing, especially in the equatorial zone. Figure 6 shows the change in maximum temperature between 1945 and 2014, which indicates an increase in the hot spots discussed above–South India, Sri Lanka, and Central America.
The temperature increase in recent decades and in the future also leads to evaporative loss of water that will compound the reduction in water availability.
Worldwide annual maximum temperature changes. Change in annual maximum temperature from 1945 to 2014 (top panel) and the average annual maximum temperature during 1945–2010 (bottom panel). From the US National Oceanic and Atmospheric Administration, Earth System Research Laboratory, Boulder, Colorado (public domain). Data definition as shown in Figure 1. EQ, equator; Tmax, annual maximum temperature.
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Journal information: JAMA Network Open
