7 Detailed information on survey methods can be found elsewhere. Data were age-adjusted to the 2000 US standard population using age strata of 18–44, 45–64 and 65–76.
#MATLAB R2015A DREAMSPARK UNIVERSITY OF UTAH PROFESSIONAL#
18 The diabetes incidence rate was self-reported via the Behavioral Risk Factor Surveillance System (BRFSS) and defined as the rate of adults (18–76 years) who reported to be told by a health professional in the last year they had diabetes (type 1 or 2). Via the National Diabetes Surveillance System of the Centers for Disease Control and Prevention (CDC), age-adjusted diabetes incidence rates per 1000, along with the corresponding 95% CI, were available for all states and territories per year. We specifically hypothesized that diabetes incidence and prevalence of glucose intolerance increase with rising outdoor temperatures.ĭata on diabetes incidence in 50 states of the USA and 3 territories (ie, Guam, Puerto Rico and Virgin Islands) were available for the years 1996–2013. Therefore, in the present study, we aimed to assess the association between outdoor temperature and glucose metabolism on a countrywide as well as a global scale. However, the importance of this association, especially in relation to the increasing diabetes burden, has never been studied on the population level. Recently, a positive association was found between outdoor temperature and glycated hemoglobin (HbA1c), 17 indicating that systemic glucose homeostasis is influenced by environmental temperature. 14–16 Considering the putative role of BAT in the control of insulin action, combined with the effect of ambient temperature on BAT activity, we hypothesized that the global increase in temperature contributes to the current type 2 diabetes epidemic. It has previously been shown that BAT activity is negatively associated with outdoor temperature and is highest in winter. 12 It is conceivable that an increased flux of fatty acids toward BAT will result in a compensatory increased flux of glucose to other metabolically active tissues, thereby improving systemic insulin sensitivity. 11 A recent landmark paper showed that acclimatization of patients with type 2 diabetes to moderate cold for only 10 days already improved insulin sensitivity as determined by a markedly higher glucose infusion rate during a hyperinsulinemic–euglycemic clamp, while body weight was unaltered. 9 10 Indeed, prolonged cold acclimatization recruits BAT activity 10 and is able to induce modest weight loss. 8 Physiologically, BAT is activated by cold exposure. Recently, brown adipose tissue (BAT) has emerged as an organ that is capable of combusting large amounts of lipids to generate heat. 6 Interestingly, a very low-calorie diet can rapidly diminish steatosis and insulin resistance independent of weight loss 7 indicating dissociation between insulin resistance and obesity perse. 3–5 For example, South Asians are prone to develop type 2 diabetes at a relatively low BMI, presumably because of the limited lipid storage capacity of their adipose tissue depots. 3 The variability in the degree of steatosis and the heterogeneity of body fat distribution over subcutaneous and visceral fat depots probably explains the only modest association between measures of overall body fat and insulin resistance. However, according to the lipid overflow hypothesis, when the storage capacity of adipose tissue is exceeded, lipids can accumulate in organs (steatosis) including the pancreas, liver, heart and skeletal muscle, resulting in insulin resistance of those organs. With increasing body mass index (BMI), glucose and lipids are initially stored in expanding (subcutaneous) adipose tissue compartments. 1 The type 2 diabetes epidemic accompanies the increasing prevalence of obesity. 1 In high-income countries, 91% of adults affected by diabetes have type 2 diabetes. In 2015, 415 million adults globally were suffering from diabetes, and expectations are that the prevalence will rise by almost 55%, up to 642 million cases by 2040. The prevalence of type 2 diabetes is increasing rapidly worldwide.