- A study links diabetes and climate change, but one expert says the findings do not imply causation
- Heat waves, infectious diseases and food shortages are among climate change-related public health concerns
“We were surprised though by the magnitude of the effect size,” said Lisanne Blauw, a researcher at Leiden University Medical Center in The Netherlands and lead author of the study.
“We calculated that a 1-degree Celsius rise in environmental temperature could account for more than 100,000 new diabetes cases per year in the USA alone,” she said. “Future research into the effects of global warming on our health status is therefore of great importance.”
“I think calorie consumption and weight are probably the biggest by a country mile,” said Dr. Adrian Vella, an endocrinologist who has researched Type 2 diabetes at the Mayo Clinic. He was not involved in the new study.
“I think the general message always should be that association studies do not actually imply causation,” he said of linking climate change and diabetes.
The worldwide prevalence of glucose intolerance rose by 0.17% per 1-degree Celsius increase in temperature, the researchers found.
“To the best of our knowledge, this study is the first to assess the association of outdoor temperature with diabetes incidence and the prevalence of raised fasting blood glucose on a national and global level,” the researchers wrote.
“The function of brown fat tissue is to burn fat to generate heat, which is important to prevent a decline in body temperature during cold exposure. Therefore, we hypothesize that brown fat plays a role in the mechanism underlying the association between outdoor temperature and diabetes,” Blauw said. “In warmer climates, brown fat may be less activated, which may causally lead to insulin resistance and diabetes.”
On the other hand, Vella said that brown fat doesn’t have that much of an impact on metabolism in humans.
“In humans, brown adipose tissue likely explains about 1% or 2% of energy expenditure in cold situations, and shivering explains far more, so it’s an exaggeration,” he said.
“Between 1996 and 2009, I believe the environment has changed,” he added. “Lots of things changed that might change diabetes incidence, right? The actual population composition changed a little bit. The caloric consumption of that population likely changed. We don’t know about physical activity.”
“In hotter temperatures, dehydration and heatstroke increases morbidity and mortality in people with diabetes. People with diabetes are predisposed to cardiovascular events during heat waves and higher mortality from heart attack on days of high air pollution,” according to the report.
Meanwhile, an increased prevalence of diabetes may lead to more carbon emissions being generated by the health care systems treating those patients.
“Diabetes-related complications — such as (cardiovascular disease), stroke and renal failure — cost lives and money. Hospitalizations from such complications are also energy-intensive and increase (greenhouse gas) emissions,” according to the report.
In the executive summary, the authors wrote, “We — physicians in medical societies representing over half of the nation’s doctors — see a need to share our growing understanding and concern about the health consequences of climate change with all Americans.”