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Global Warming and Diabetes

Incidence of diabetes linked to rising temperatures

Diabetes is on a rapid rise, with estimates of 642 million diabetes patients by the year 2040, a 55% increase from 2015. Scientists have begun to question whether the increasing global temperature could have any correlation with diabetes incidence and glucose intolerance.

Previous studies have shown that exposing patients to a colder temperature for as short as 10 days can improve insulin sensitivity due to activation of brown adipose tissue (BAT). BAT, considered the body’s good fat, is known to convert lipids into body heat.  By increasing the mobility of fatty acids towards BAT, glucose transport is increased to other metabolically active tissues. Researchers hypothesized that increasing global temperatures could correspond to a negative impact on BAT activity, thus leading to an increase in type 2 diabetes and glucose intolerance worldwide. Using a patient population residing in the 50 U.S. states, Puerto Rico, Guam, and the Virgin Islands from 1996-2013, researchers used the National Diabetes Surveillance System of the Centers for Disease Control to find state and territory specific incidence of diabetes. A meta-regression analysis was performed from each separate state/territory to find the association between temperature and age-adjusted diabetes incidence rates. A worldwide meta-regression analysis was also performed to analyze the global correlation in 190 countries between prevalence of rising blood glucose, average annual temperature, and income data from the World Bank income group. A separate meta-analysis was performed to account for body weight by amalgamating obesity prevalence and incidence of type 2 diabetes and using the diabetes adjusted obesity rate to determine association between temperature and diabetes incidence rate.

Researchers found the incidence of diabetes rose with an increase in higher mean annual temperature, with the overall estimate of effect being 0.314 (95% CI 0.194 to 0.434) per 1,000 for every 1 degree Celsius increase. Obesity rate was also increased by 0.173% (95% CI 0.050% to 0.296%) per degree Celsius.  Globally, when adjusting for age, sex, and income, there was an increase in fasting blood glucose levels by 9.65% (95% CI 9.11% to 10.13%) and obesity by 19.51% (95% CI 17.94% to 21.07%). The incidence of raised fasting blood glucose increased by 0.170% (95% CI 0.107% to 0.234%) for every increase in degree Celsius, and a similar increase was noted in obesity with a 0.295% (95% CI 0.137% to 0.454%). On a state level, occurrence of diabetes was higher in warmer states that had a positive mean change in annual temperature  (Puerto Rico, West Virginia, and South Carolina) compared to cooler states that had a negative mean change in annual temperature (Minnesota, Massachusetts, and Colorado).

Although an association was found between incidences in diabetes, rising glucose intolerance, and increase in mean average temperature, one cannot question weakness in the studies. Temperature is an uncontrollable variable and cannot be used to serve as a bias.  Likewise, an increase in temperature cannot be singled out when there is a global decline of a healthy diet and active lifestyle. This observational study was also unable to adjust for possible confounders. Further research is still needed to establish an association between environmental changes and increased incidence of disease, such as type 2 diabetes.

What can rising temperatures mean for patients who have already been diagnosed with type 1 or type 2 diabetes? Diabetes patients are affected more by heat than the average healthy population. Damage to blood vessels and nerves can affect sweat glands, causing the body to cool inefficiently. High temperatures also change how the body uses insulin and increases the risk of dehydration due to water loss from sweat and by not drinking enough water leading to increased blood sugars that cause increased urination. Patients should be made aware of the risks, and educated to increase water consumption and rest appropriately.

Practice Pearls:

  • An increase in global temperature may cause an increase in incidence of diabetes due to the inactivation of brown adipose tissue.
  • Geographical region could correlate to obesity and development of diabetes.
  • People with diabetes are more sensitive to warmer temperatures and should be advised to stay well hydrated.

References:

Managing Diabetes in the Heat.” Centers for Disease Control and Prevention. 29 June 2016. Web. 07 Apr. 2017.

Nordqvist, Christian. “Brown fat: What is it and can it help reduce obesity?” Medical News Today. MediLexicon International, n.d. Web. 07 Apr. 2017.

Blauw, Lisanne L., N. Ahmad Aziz, Martijn R. Tannemaat, C. Alexander Blauw, Anton J De Craen, Hanno Pijl, and Patrick C N Rensen. “Diabetes incidence and glucose intolerance prevalence increase with higher outdoor temperature.” BMJ Open Diabetes Research & Care 5.1 doi: 10.1136/bmjdrc-2016-000317 (2017): Web.

 

Tenzing Dolkar, BSc., PharmD Candidate 2017, Lake Erie College of Osteopathic Medicine, School of Pharmacy