Higher temperatures contribute to dehydration, which increases the risk of kidney stones in those people predisposed to the condition, a new study has found.
Researchers at The Children’s Hospital of Philadelphia examined 60,000 patients in several cities across the U.S., with varying climates, discovering a link between hot days and kidney stones.
The study raises the theory that as the planet warms up climate change is taking its toll on human health.
Lead researcher and urologist, Gregory Tasian, said: ‘We found that as daily temperatures rise, there is a rapid increase in the probability of patients presenting over the next 20 days with kidney stones.
The team analysed medical records of more than 60,000 adults and children with kidney stones between 2005 and 2011 in Atlanta, Chicago, Dallas, Los Angeles and Philadelphia as well as weather records for each city.
They recorded the risk of stone presentation for the full range of temperatures in each city.
As average daily temperatures rose above 10°C, the risk of a person getting kidney stones increased in all cities, except LA.
The delay between a person being out in the hot weather and developing stones was short, peaking within three days of exposure to high temperatures.
‘These findings point to potential public health effects associated with global climate change,’ said Mr Tasian.
‘However, although 11 per cent of the U.S. population has had kidney stones, most people have not.
‘It is likely that higher temperatures increase the risk of kidney stones in those people predisposed to stone formation.’
Higher temperatures increase the risk a person will become dehydrated, which leads to a higher concentration of calcium and other minerals in the urine, which cause stones to grow in the kidneys.
It is a painful condition, which causes around 500,000 patients to visit emergency departments across the U.S. each year.
And the number of cases has increased markedly across the world in the last 10 years.
While stones remain more common in adults, the numbers of children developing kidney stones has soared in the last 25 years.
Kidney Stones in Children: An Epidemic
The factors causing the increase in kidney stones are currently unknown, but are thought to be influenced by changes in diet and fluid intake.
When stones do not pass on their own, surgery is often necessary.
The new study also found extremely low temperatures increased the risk of kidney stones in three cities – Atlanta, Chicago and Philadelphia.
The researchers said low temperatures causes more people to stay inside in the warm, causing changes in diet and decreased exercise levels, which could increase risk of stone formation.
They argued that the number of hot days in a year, may better predict the risk of a person suffering kidney stones, compared to the average annual temperature.
Atlanta and LA share the same annual temperature, of 17°C, but Atlanta has more hot days than LA – as well as twice the prevalence of kidney stones.
Tasian added that while the five cities chosen for their study are representative of those found across the world, more research is needed to explore the current findings.
Future studies should examine how risk patterns vary in different populations, including among children, which only represented a small percentage of those analysed in the current study.
The team’s findings have a broader context, in the patterns of global warming.
The authors note that other scientists have reported overall global temperatures between 2000 and 2009 were higher than 82 per cent of temperatures over the last 11,300 years.
Furthermore, increases in greenhouse gas emissions are expected to raise Earth’s average temperatures by 1 to 4.5°C by 2100.
Tasian added: ‘Kidney stone prevalence has already been on the rise over the last 30 years, and we can expect this trend to continue, both in greater numbers and over a broader geographic area, as daily temperatures increase.
‘With some experts predicting that extreme temperatures will become the norm in 30 years, children will bear the brunt of climate change.
The study was published in the journal of the National Institute of Environmental Health Sciences.