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Higher outdoor temperatures associated with IGT, diabetes incidence
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A rise in temperatures across the United States and globally may be driving an increase in both diabetes incidence and impaired glucose tolerance worldwide, according to findings from a Dutch study.
“In this study, we showed that an increase in outdoor temperature is related to an increase in new diabetes cases in the United States,” Lisanne L. Blauw, BSc, a PhD student in the division of endocrinology, department of medicine at Leiden University Medical Center in the Netherlands, told Endocrine Today. “On the global level, a higher outdoor temperature was associated with an increase in glucose intolerance.”
Blauw and colleagues analyzed data on diabetes incidence and obesity prevalence for each U.S. state and territory between 1996 and 2013, using information from the National Diabetes Surveillance System of the CDC and data on the mean annual temperature per state from the National Centers for Environmental Information. Worldwide, researchers assessed countrywide prevalence rates for IGT and obesity using data from the WHO’s Global Health Observatory online data system, as well as countrywide mean annual temperature data for 2014 from the Climatic Research Unit of the University of East Anglia. Researchers used meta-regression analyses to assess any association between mean annual temperatures and prevalence of diabetes and IGT.
In the United States, both diabetes incidence rate and obesity increased with higher mean annual temperatures; overall effect estimate for the association was 0.314 (95% CI, 0.194-0.434), indicating an age-adjusted diabetes incidence increase of 0.314 per 1,000 for each degree Celsius increase in mean annual temperature. Obesity prevalence in the United States increased by 0.173% for each degree Celsius increase in mean annual temperature.
Worldwide, researchers observed a similar trend. The prevalence of IGT increased by 0.17% for each degree Celsius rise in temperature across 190 countries (95% CI, 0.107-0.234); obesity prevalence increased by 0.295% for each degree Celsius rise in temperature (95% CI, 0.137-0.454).
Associations persisted after adjustment for obesity, according to the researchers, with the U.S. diabetes incidence rate increasing by 0.29 per 1,000 (95% CI, 0.164-0.416).
“Based on our results, a 1°C rise in environmental temperature would account for over 100,000 new diabetes cases per year in the [United States] alone, given a population of nearly 322 million people in 2015,” the researchers wrote. “These findings emphasize the importance of future research into the effects of environmental temperature on glucose metabolism and the onset of diabetes, especially in view of the global rise in temperatures with a new record set for the warmest winter in the [United States] last year.”
Blauw noted that the activation status of brown fat may be lower in warmer climates, which may causally lead to insulin resistance and diabetes.
“Our study is an observational study, and for that reason we cannot prove a causal link between outdoor temperature and diabetes,” Blauw told Endocrine Today. “However, based on our study results and in the light of global warming, we regard it highly important to do further research into the effects of environmental temperature, not only on the environment, but also on our health status.” – by Regina Schaffer
For more information:
Lisanne L. Blauw, BSc, can be reached at the division of endocrinology, department of medicine, Leiden University Medical Center, Leiden, the Netherlands; email: l.l.blauw@lumc.nl.
Disclosure: The researchers report no relevant financial disclosures.
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