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 Global warming has increased temperatures overall by nearly 1 degree
Celsius (just under 2 degrees Fahrenheit) over the past century, and
they are expected to rise by another 3 to 4 degrees C by the end of
this century, the authors write. Heat waves have also become more
common, with about three quarters of the increase blamed on climate
change, they add.
“There’s evidence that long periods of heat waves have increased
more significantly with climate change, when it’s extremely hot the
risk for kidney damage begins to really become evident,” said senior
study author Dr. Richard Johnson of the University of Colorado,
Denver.
Extreme heat exposure can have immediate health effects, causing
dehydration, heat exhaustion and heat stroke, as well as worsening
pre-existing chronic disease, which can be fatal, Johnson and his
colleagues write in the Clinical Journal of the American Society of
Nephrology.
Although chronic kidney disease is often caused by diabetes or high
blood pressure, it can also be the result of recurrent heat exposure
with physical activity and not enough hydration, which puts a heavy
strain on the kidneys.
Chronic kidney disease often has no symptoms and has to be diagnosed
by blood test. In early stages it may be treated with medications,
but as kidneys fail over time they may require dialysis to filter
the blood, and ultimately they can fail entirely, leading to death
or kidney transplant.
Johnson and his coauthors studied reports of upticks in cases of
chronic kidney disease detected in hot climates and among
populations without regular access to healthcare, such as poor
agricultural workers.
A recent epidemic of chronic kidney disease in Central America,
particularly among male sugarcane workers on the Pacific coast, was
initially suspected to be linked to chemicals or other toxins, for
example. But the kidney damage was found to be more common among
sugarcane cutters than among pesticide applicators, and less common
at higher altitudes where temperatures are cooler - suggesting that
workers with the greatest exertion and heat exposure had the highest
risk.
A similar epidemic is currently affecting about 100,000 individuals
in northern Sri Lanka, primarily among young to middle-aged male
rice farmers and women working in the fields, the authors write.
Still another epidemic is affecting Andhra Pradesh on the
southwestern coast of India, an area with some of the longest heat
waves in the country.
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Heat waves occur when sustained temperatures reach 40 degrees C (104
degrees F), or the temperature increases by 5 to 6 degrees C over
the normal maximum temperature of the region or any time
temperatures reach 45 degrees C (113 degrees F) or greater.
“It is undeniable that there will be numerous direct and indirect
health effects as a result of climate change,” said Rebecca Laws, a
postdoctoral associate at Boston University School of Public Health
who was not part of the new study. “We could be witnessing one such
direct health effect, as epidemics of (chronic kidney disease)
become more apparent in hot and humid regions throughout the world,”
she said.
“To better understand potential implications from climate change, we
need to conduct more research to determine the role of heat stress
and dehydration in each geographic region, as well as identify the
underlying biological mechanisms,” Laws told Reuters Health by
email.
Similar epidemics may be ongoing in the hotter regions of Africa and
the Middle East, and improving hydration and worksite practices may
help prevent some heat related cases of chronic kidney disease, the
authors write. But more studies are needed to determine whether
there is a cause and effect relationship at work.
“There’s enough here to warrant concern that heat stress and
dehydration could be a real problem for poor people working in the
field,” Johnson told Reuters Health.
“I think improving hydration and providing shade can be recommended
now,” he said. “Will it prevent this epidemic? That needs to be
tested.”
SOURCE: http://bit.ly/1qe2hbO Clinical Journal of the American
Society of Nephrology, online May 5, 2016.
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