Climate change: A challenge for kidneys and sperm?

The German Society for Urology (DGU) warns of a long-term increase in urological diseases as a result of climate change and its increasingly occurring extreme heatwaves.

The August 2020 heatwave in Europe raised alarms once again

In COVID-19 times, climate change and its effects on human health have been pushed into the background in public opinion. In view of the most recent heatwave that took place in Europe in August 2020, however, the German Alliance for Climate Change and Health, the Healthy Earth Foundation, the Health for Future Alliance and the head of the German Green Party, Robert Habeck, are calling for a comprehensive plan to protect health in this worsening trend.

 "The health consequences of more frequent extreme heat and higher average temperatures are not limited to an increase in strokes, heart attacks, or infectious diseases. They also increase the risk of urological diseases, from urinary stones to severe kidney damage," says Prof. Dr. Jens Rassweiler, President of the German Society of Urology. (German acronym: DGU).

Various climate-sensitive diseases are increasingly expected in everyday urology  "Heat-induced dehydration of the body impairs the water and blood-salt balance and leads to a decrease in kidney function. The resulting volume depletion and hyperosmolarity favor more frequent stone formation. In addition, empirical data suggest that heat-related risks of postoperative wound infections will also increase. At present, however, I do not see any need for Germany to postpone certain urological surgeries to cooler months," says Prof. Dr. Joachim Steffens. As a further effect of rising temperatures, the head physician of the Department of Urology and Pediatric Urology at the St. Antonius Hospital in Eschweiler, Germany, also believes that male fertility might be impaired because heat reduces sperm quality.

Kidney as a protective organ... and target organ from heat-associated damage

Some urologists are paying more attention to temperature-related kidney diseases. "The kidneys play a central role in protecting humans from heat-related consequences but are also themselves the target organ of heat-related damage. The spectrum ranges from acute kidney damage, an increased incidence of kidney stones and urinary tract infections to chronic kidney damage," says Prof. Dr. Ralph Kettritz, specialist for internal medicine and nephrology at the Charité University Clinic in Berlin.

It is a particular challenge for the kidneys to preserve blood salts (electrolytes) and water in the body under extreme heat conditions and to maintain a state of equilibrium in terms of quantity and concentration. If this is not successful, the body loses important substances, and the renal blood flow decreases. In addition, there is a maximum stimulation of the antidiuretic hormone (ADH, also known as vasopressin) to preserve water. These mechanisms are involved in the development of acute kidney injury (AKI).  

"Water conservation is achieved by a maximum concentration of urine through ADH. The resulting reduced urine flow favors ascending infections in the urinary tract. In addition, stone formation (urolithiasis) is promoted in highly concentrated urine," said Prof. Dr. Kettritz. Initial data from the US National Academy of Sciences already indicate that the heat-related kidney stone "risk belt" region is expanding into the northern latitudes of the USA.

Interdisciplinary research networks, a crucial step forward

The formation of interdisciplinary research networks is important for generating knowledge about the urological consequences of climate change. Urologists are also concerned with the andrological question of a connection between rising average temperatures and a conceivable increase in infertility among men in the northern regions. Prof. Dr. Steffens: "An increased ambient temperature of the testicles reduces sperm quality and can thus impair male fertility. 

Evolution has placed the male testicles outside the body cavity since the temperature there is two to three degrees lower than the body core temperature of 37 degrees, which leads to good sperm quality". It is known that a varicocele, for example, increases the temperature in the scrotum and thus demonstrably promotes infertility. This temperature-related disease process in varicocele could possibly also be transferred to a temperature-related increase in infertility as a result of climate change. However, there is as yet no scientific data on this, nor on questions concerning presumably special genetic dispositions for unrestricted fertility in men who are constantly exposed to high temperatures in the equatorial climate zone.

Prof. Dr. Joachim Steffens, therefore, sees an urgent need for corresponding scientific findings. "There is still no systematic research on the influence of global warming on diseases of the urinary tract and the male reproductive organs," said the former DGU president. He encourages the formation of interdisciplinary research alliances, such as with nephrology, in order to generate knowledge about the urological consequences of climate change.