This is a plain English summary of anoriginal research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.

Acute kidney injury is more likely in hot weather, a data analysis found. The risk:

• increased as the maximum daily temperature rose (especially above 25 degrees Celsius)
• was 62% more likely at 32 degrees than at 17 degrees.

The researchers suggest that when hot weather is forecast, clinicians advise people at risk of kidney injury to drink plenty of water, and avoid caffeinated drinks (including tea and coffee).

More information about acute kidney injury can be found on the NHS website.Advice about staying safe in hot weather can be found on the Government website.

The issue: is acute kidney injury more likely during hot weather?

Acute kidney injury means that the kidneys have stopped working properly. It is usually caused by other serious illnesses, includingheart attack and sepsis, and can occur in people who do not have kidney disease. According to theUK Kidney Association, acute kidney injury is linked with about 100,000 deaths every year in hospital in the UK.

Studies in hot environments have found a link between hot weather and kidney problems related to dehydration, for example kidney stones and acute kidney injury. Acute kidney injury iscommon in people with heatstroke; milder heat-related illnesses (such as exhaustion and fainting) also increase the risk.  

In the UK, people with diagnosed kidney disease, and those at risk (because of diabetes or high blood pressure, for example) have their kidney function regularly monitored. On admission to hospital, people have their kidney function checked, and compared to previous readings in their records. If there is a marked drop in kidney function compatible with acute kidney injury, a patient safety alert is sent to the treating physician, and a copy to theUK Renal Registry.

Researchers used this registry to explore the link between hot weather in the UK and acute kidney injury episodes.

What’s new?

The researchers linked the date and location of more than 1.3 million episodes of acute kidney injury recorded by the UK Renal Registry between April and September from 2017 to 2021. They explored whether the incidents corresponded with daily maximum temperatures.

The effects of heat on acute kidney injury were highest in July. For example, during a 7-day heatwave in July 2021, acute kidney injury increased dramatically (by 29%).

The risk of acute kidney injury:

• increased as the maximum daily temperature rose (especially above 25 degrees Celsius)
• was apparent even at mild temperatures
• was much more likely (62% more likely) at 32 degrees than at 17 degrees.

People with more advanced kidney injury had a lower risk of heat-related episodes. The authors say this group is more likely to be in hospital and therefore could be less affected by the temperature outdoors.

Why is this important?

The findings show that the risk of acute kidney injury increases when temperatures are high. They support public health advice to keep cool in hot weather, especially for people at risk of dehydration or kidney disease.

The risk of heat-related acute kidney injury was highest in 2020 and 2021. The researchers say this could have been driven by the pandemic, because people at risk of acute kidney injury were also at high risk from COVID-19, and were more likely than others to be in hospital. Data were anonymised, so researchers could not investigate whether the link between acute kidney injury and temperature was influenced by age, sex, other conditions or medication use.

What’s next?

Clinicians may be aware that some people are at increased risk of acute kidney injury during hot weather because of chronic kidney disease, diabetes or heart failure. But at present, clinicians do not routinely discuss the weather with patients.

Even small changes in kidney function can affect outcomes. The researchers suggest that clinicians advise people with kidney disease to take precautions in warm weather, and:

• drink more water
• avoid caffeinated drinks.

You may be interested to read

This is a summary of: Hajat S, and others.Ambient heat and acute kidney injury: case-crossover analysis of 1354675 automated e-alert episodes linked to high-resolution climate data.Lancet Planetary Health 2024; 8: e156–162.

A paper describing the impact of climate change on people with kidney disease. Barraclough KA, and others.Climate change and kidney disease—threats and opportunities.Kidney International 2017; 92: 526 – 530.

A paper examining the effect of heat extremes on kidney disease. Johnson RJ, and others.Climate change and the kidney.Annals of Nutrition and Metabolism 2019; 74: 38 – 44.

A blog written about this paper by theUK Kidney Association.

A summary on the NIHR Evidence website about what to do when the temperature increases:Hot weather health warnings are not getting through to people at risk.

Funding: This study was funded by theNIHR Health Protection Research Unit in Environmental Change and Health.

Conflicts of Interest: No relevant conflicts were declared. Full disclosures are available on theoriginal paper.

Disclaimer: Summaries on NIHR Evidence are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that the views expressed are those of the author(s) and reviewer(s) at the time of publication. They do not necessarily reflect the views of the NHS, the NIHR or the Department of Health and Social Care.

NIHR Evidence is covered by thecreative commons, CC-BY licence. Written content and infographics may be freely reproduced provided that suitable acknowledgement is made. Note, this licence excludes comments and images made by third parties, audiovisual content, and linked content on other websites.

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UK Kidney Association

“We contributed data to this important study to investigate how heat impacts on acute kidney injury and were surprised to find that the risk already increases at 25 degrees Celsius.

It is important that people at risk of or living with kidney disease are aware that they are vulnerable to hot weather, and to discuss individual measures to prevent acute kidney injury on hot days with their doctors. We are planning to do future research on how to better prevent heat related acute kidney injury.”

Dorothea Nitsch, Director of Research, UK Renal Registry of the UK Kidney Association

Lived experience

“I have advanced kidney disease and am therefore at risk of acute kidney injury. This is a timely reminder to me to manage my hydration during at risk periods.

This study encompasses data from community and hospital settings, some of which may previously have been overlooked. The findings could be used most effectively in the community. People at risk of acute kidney injury could be given tailored advice and contacted with alerts during periods of increased temperatures.”

Angela Watt, Public Contributor, North Shields

Consultant kidney doctor

“I care for people with acute kidney injury, and those at increased risk of developing it. Acute kidney injury is often under-diagnosed in the community, but can have severe consequences, including death, if it is not properly managed. Better understanding that outdoor temperatures can increase risk (as this research found) could potentially lead to an earlier diagnosis when people present to medical services, and ensure that they receive optimised care.”

James Burton, Professor and Honorary Consultant in Renal Medicine, Leicester Hospitals, and Clinical Vice President of the UK Kidney Association

Consultant kidney doctor

“This research suggests that as global temperatures rise, as a result of climate change caused by humans, acute kidney injury is likely to become more common. It implies rising demand on clinical services worldwide.

During heatwaves in the UK, increasing numbers of people with acute kidney injury may put pressure on clinical services. This is relevant to clinical practice, design of local and national clinical services (renal and general medical) and to the research we need to intervene to reduce these risks. We need to design and implement public health interventions to reduce the harm associated with heat.”

Dominic Taylor, Consultant kidney doctor, North Bristol NHS Trust and University of Bristol