A spike in hospitalizations for a dangerous low-salt condition is the latest in a growing list of health threats linked to climate change.
An average global temperature increase of 3.6 degrees Fahrenheit could lead to a 14% increase in hospitalizations for critically low sodium levels in the blood, a condition called hyponatremia, according to a Swedish study.
Hyponatremia can be caused by diseases such as heart, kidney and liver failure, as well as from excessive sweating or fluid intake that dilutes sodium (salt) concentrations in the blood.
Sodium is needed to maintain normal blood pressure, support nerve and muscle function and regulate fluid balance in and around cells. A significant drop in blood sodium levels can trigger nausea, dizziness, muscle cramps, seizures and even coma.
Hyponatremia cases increase in the summer months, but the impact of warming temperatures due to climate change was unclear.
To learn more, researchers at the Karolinska Institute in Solna, Sweden, analyzed nine years of data on Swedish adults and identified more than 11,000 hospitalizations for hyponatremia. Most were women. Their median age was 76, meaning half were older, half younger.
The risk was nearly 10 times higher on the hottest days than on the coolest days, with women and the elderly having highest odds. Those 80 and older were 15 times more likely to be hospitalized for hyponatremia during heat waves.
Cases were largely stable from 14 to 50 degrees F but increased rapidly when the temperature climbed above 59 degrees F.
Researchers applied the data to a model forecasting global warming of 1.8 to 3.6 degrees F, which matches projections for 2050 from the United Nations' Intergovernmental Panel on Climate Change.
The results showed that hospital admissions due to hyponatremia could increase by 6.3% with a 1.8 degree F increase and by 13.9% with a 3.6 degree F increase, according to the study recently published in The Journal of Clinical Endocrinology and Metabolism.
"Our study is the first to provide precise estimates of how temperature influences the risk of hyponatremia, findings that could be used to inform health care planning for adapting to climate change," said first author Buster Mannheimer, an adjunct senior lecturer in Karolinska's Department of Clinical Science and Education. He spoke in an institute news release.
"We believe these estimates are quite conservative seeing as we didn't account for secondary diagnoses of hyponatremia, extreme weather events or an aging population," said study co-author Jonatan Lindh, an associate professor of laboratory medicine. "Without adaptive measures, this suggests that over the next decades rising global temperatures alone will increase the burden of hyponatremia on health care systems."
The National Kidney foundation has more on hyponatremia.
SOURCE: Karolinska Institute, news release, March 8, 2022