Global warming caused more than 200,000 cases of kidney disease in Brazil in 15 years, says study

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It is already known that changes in the environment can influence the health of people and animals. Air pollution, contaminated water and soils, prolonged drought and other environmental factors affect both development and basic issues such as water and oxygen consumption.

However, measuring the direct effect of climate change on organs was seen as almost impossible by scientists. So far.

For the first time, a large study was able to identify more than 200,000 cases of kidney disease caused directly by the influence of temperature. In addition, extreme temperature variations in the same day — such as cold nights and intense heat during the day — can affect the body for up to two days afterwards.

The risk of developing some type of kidney problem was higher in children aged zero to 4 years is higher, 3.5% for every 1˚C increase in temperature, in women (1.1%) and in people over 80 years (1%).

The research, which sheet had access, was published in this Sunday’s issue (31) of The Lancet Regional Health – Americas.

The study, conducted in partnership between Monash University in Melbourne, Australia, and the Institute for Advanced Studies (IEA), at the University of São Paulo, evaluated data from 2,726,886 hospitalizations for some type of kidney disease among patients. years 2000 and 2015 in 1,816 Brazilian municipalities.

The so-called attributable risk (that is, that actually occurs in an individual, different from the calculated relative risk for a population) of kidney disease associated with temperature rise was 7.4%, equivalent to 202,093 cases.

To make the association between temperature and kidney damage, the researchers evaluated the historical period of temperature in each of the cities and cross-referenced with the records of hospital admissions for kidney disease in the SUS (Unified Health System).

After analyzing the historical series, the researchers adjusted the models for different variables, such as age, sex, wage income and place of residence. “Since the municipalities were evaluated by themselves, we were able to identify the difference in temperature directly influencing the case of kidney disease”, explains the meteorologist, a researcher at the Faculty of Medicine at USP and a collaborator at the University of Monash, Micheline Coelho.

The pathologist and professor at the IEA-USP, Paulo Saldiva, who also participated in the study, explains how heat directly affects the kidneys and how the effect is greater in children and women. “Variations of heat can increase the risk of ‘decompensating’ preexisting chronic diseases, such as diabetes, blood pressure. In addition, it also acts by regulating transpiration, absorbed water volume and urine production,” he says.

“Very young children still do not have a well-developed renal system and the surface mass ratio favors heat exchange with the environment. Women, especially postpartum women, are more prone to urinary infections, which, in an environment of dehydration, by heat, it can affect the kidneys.”

The fact of having included the 1,816 municipalities that concentrate almost 80% of the Brazilian population allows us to make an adequate cut of the so-called chronic kidney disease epidemic in the country. “This is one of the few large-scale studies that show the effects of global warming on kidney diseases, and it was only possible to do it because we have the SUS database”, says Saldiva.

This also made it possible to draw an overview of risk by region of the country. “In the Southeast, the risk was lower, 0.7%, while the North region had the highest risk, 2.2%. This was expected because the North region is warmer and not only hot, it is also humid, and humidity affects how we absorb heat in our body,” says Coelho.

In Brazil, chronic kidney disease causes 2.4 million deaths annually, and it is estimated that more than ten million Brazilians have the disease, a number that is possibly underreported. The prevalence of chronic kidney disease in the US is 110 per 100,000 inhabitants and, in Japan, 205 per 100,000 inhabitants.

Coelho had been researching the relationship between climate and temperature in humans for the past ten years, an area known as biometeorology. According to the World Health Organization, between 90,000 and 255,000 new deaths from chronic diseases may be directly linked to the increase in global temperature by 2030 and 2050, respectively.

“When we do a 15-year time series like this and develop an epidemiological model on top, we can capture the correlation of that disease taking into account the temperature variation. Thus, it is possible, from this analysis, to quantify how many deaths would be avoided if there was no change in temperature,” he says.

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