Abstract
Cold exposure stimulates energy expenditure and glucose disposal. If these factors play a significant role in whole body energy balance, and glucose homeostasis, it is predicted that both obesity and type 2 diabetes prevalence would be lower where it is colder. Previous studies have noted connections between ambient temperature and obesity, but the direction of the effect is confused. No previous studies have explored the link of type 2 diabetes to ambient temperature. We used county level data for obesity and diabetes prevalence across the mainland USA and matched this to county level ambient temperature data. Average ambient temperature explained 5.7% of the spatial variation in obesity and 29.6% of the spatial variation in type 2 diabetes prevalence. Correcting the type 2 diabetes data for the effect of obesity reduced the explained variation to 26.8%. Even when correcting for obesity, poverty and race, ambient temperature explained 12.4% of the variation in the prevalence of type 2 diabetes, and this significant effect remained when latitude was entered into the model as a predictor. When obesity prevalence was corrected for poverty and race the significant effect of temperature disappeared. Enhancing energy expenditure by cold exposure will likely not impact obesity significantly, but may be useful to combat type 2 diabetes.
Highlights
For ambient temperature in individual susceptibility to obesity[4,21,22], but the results are confused
Colder ambient temperatures are generally found in locations at higher latitudes, where sun exposure may be a limiting factor on vitamin D status[27], which has been implicated as a causal factor in the risk of type 2 diabetes[28,29], such a link is disputed[30]
The absence of an ambient temperature effect on obesity levels could occur for several reasons
Summary
For ambient temperature in individual susceptibility to obesity[4,21,22], but the results are confused. There are large spatial variations in levels of poverty, which is known to be a key factor linked to the risk of obesity and type 2 diabetes[23,24]. A spatial link between ambient temperature and disease prevalence may come about because of these confounding factors. To study the association between ambient temperature and variations in the prevalence of obesity and type 2 diabetes we used the county level disease prevalence data across the mainland USA (downloaded 2014) and matched these to the county level ambient temperature data. We used the US census data (2010) to control for the potential confounding impacts of poverty and race
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