Summer temperatures are already soaring in some parts of the world. The UK and Europe experienced a record-breaking heatwave in May. As extreme weather events become more common with climate change, researchers are finding health impacts.
The Allegheny Front’s Kara Holsoppe spoke with Hoimonty Mazumder, MBBS, PhD, MPH, at the University of Pittsburgh School of Public Health. She and her colleagues published a study looking at the link between a gradual rise in global temperatures and a higher risk of kidney disease. The study is published in the journal Kidney Medicine, and she completed the work as a doctoral student at the University of Memphis.
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Kara Holsopple: Your study found that the rise in global temperatures is associated with a higher risk of kidney disease. How much is the risk increased and for what conditions?
Hoimonty Mazumder: This is a systemic review. We included primary studies worldwide. Our objective was to evaluate how temperature affects kidney disease, particularly disease related to renal colic. Renal colic itself is not a disease, it is an acute manifestation of different kidney diseases, such as kidney stones and urinary tract infections. These kinds of acute manifestations are characterized by the radiating pain from the lower back to groin. Then we explored both the heat and cold temperature, but we really found most of the studies explored high temperature and the kidney outcomes. We found that for every one degree Celsius increase in temperature, the risk of having renal colic is increased 2.4%.
Kara Holsopple: How did you conduct the study? Which data did you look at?
Hoimonty Mazumder: So this is not the primary study. We actually retrieved from the existing data sets and we retrieved studies related to temperature and causes of renal colic across the world. Then we screened whether these primary studies met our eligibility criteria because we set a predefined eligibility criteria. We initially retrieved more than 900 articles and we included 26 articles that actually met our research objectives.
Kara Holsopple: I know you said that it’s a global study, but can you say a little bit about some of the countries that the studies came from?
Hoimonty Mazumder: We wanted to see the global burden of the temperature and the causes of renal colic, but interestingly, we found that all of the studies are concentrated particularly in the developed regions. We really didn’t find any study from low-income countries. So that is one of the key findings of this article. We identified one very important research gap. If you think about the Global South, that is one of the very vulnerable regions due to the temperature. So we actually don’t have right now any data or any evidence from that region. Most of the studies came from the US and China.
Kara Holsopple: I was going ask who is most at risk, but it sounds like perhaps you don’t know because there is that data gap.
Hoimonty Mazumder: Yes, the data gap is one of the very key findings of these studies and also all of the studies evaluated hospital-based data. So that is another challenge. We actually didn’t find any population-based data.
Kara Holsopple: Is age or gender a risk?
Hoimonty Mazumder: We wanted to stratify analyses based on age or gender, but there is not enough evidence in existing studies, so we couldn’t do that.
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Kara Holsopple: Can you say a little bit about how the kidneys function and contribute to our overall health and why an increase in temperature would impact their functioning?
Hoimonty Mazumder: Kidneys actually play a very key role in the human body because it maintains our body’s water balance and its main function is filtering. It actually filters out the toxic materials from the body and keeps the other essential nutrients and minerals and electrolytes which are necessary for the body.
The kidney is actually very much affected by the temperature because in exposure to high temperature people frequently get dehydrated or hypohydration. When there is no water or enough fluid in the body and at the same time exposure to temperature, it actually triggers another mechanism of the body which causes sweating. Sweating also excretes water and electrolytes from the body, bypassing the kidney. So that’s why then the kidneys actually couldn’t function well when there is less water or when the body is dehydrated. In such a condition, the urine gets more concentrated.
The kidney tissues and cells and different tissue injuries happen because of frequent dehydration and hypohydration. Also temperature itself can cause different inflammation at the kidney tissues and kidney cells. Cold temperature can also affect kidney health because when the temperature is cold, actually the thirst center in our brain doesn’t function well. So people don’t feel thirsty during very cold weather, and that actually results in hypohydration or dehydration.
Kara Holsopple: What does your finding of higher kidney disease risk with the rising global temperatures tell you about what kinds of research and care will be needed in the future?
Hoimonty Mazumder: We need more population-based studies. Without a longitudinal study, we cannot actually see the long-term effects or short-term effects of temperature at the population level.
Kara Holsopple: Longitudinal study would be sort of over time in a population.
Hoimonty Mazumder: Yes. So I think that more longitudinal studies related to temperature and kidney health is very, very essential to undertake, then also we should explore more environmental and more advanced studies to understand the underlying biological mechanism of temperature and kidney health because that’s still not very well established. We have been witnessing the frequent temperature rise. So the government and the existing health system should prepare themselves during extreme heat conditions at their facilities or at the community level for the vulnerable population, especially the aging populations and those populations with existing co-morbidities. I think these are the very important steps right now.
