Influence of environmental temperature on risk of gestational diabetes

Abstract

The impact of climate variability on health has become increasingly relevant given the global rise in air temperatures over the past century.1,2 Extreme weather patterns can adversely influence health -directly, as in the case of hyperor hypothermia -and indirectly, by triggering respiratory exacerbations, infectious outbreaks, water-borne diseases and injuries. However, there is also growing evidence supporting a link between air temperature, metabolic function and energy expenditure. Brown adipose tissue aids with acclimatization to cold through its unique ability to generate heat by uncoupling cellular respiration from mitochondrial adenosine triphosphate (ATP) synthesis.4-6 Based on findings from studies involving animals and humans, the effects of brown adipose tissue activation extend beyond thermogenesis, by influencing whole-body metabolism and possibly overall body weight.7-18 Small intervention trials involving humans have suggested that even mild exposure to ambient cold -such as lowering a thermostat from 24°C to 19°C -can increase activity of brown adipose tissue by 30%-40%, resulting in substantial improvements in insulin sensitivity. [15][16][17][18] In theory, greater insulin sensitivity should improve glucose handling, but whole-population studies evaluating the potential for cold exposure to reduce glucose mishandling are lacking.We examined the impact of variation in outdoor air temperature on the risk of gestational diabetes mellitus, a transient form of diabetes arising by midpregnancy. Placental hormones lead to a temporary state of insulin resistance, starting in the second trimester of pregnancy and continuing until delivery.19 Gestational diabetes mellitus arises when the compensatory increase in insulin production fails to maintain normal blood glucose levels. This condition affects more than 15 million pregnancies worldwide each year 20 and can have serious consequences for mother, baby and the delivery process. [21][22][23] Hence, gestational diabetes mellitus offers an opportunity to study the short-term effect of ambient outdoor temperature on human metabolism. ABSTRACT BACKGROUND: Cold-induced thermogenesis is known to improve insulin sensitivity, which may become increasingly relevant in the face of global warming. The aim of this study was to examine the relation between outdoor air temperature and the risk of gestational diabetes mellitus.

Seasonal variations in incidence and maternal–fetal outcomes of gestational diabetes

“…Our finding that glucose levels in pregnancy varied with ambient temperature is in keeping with a number of previous studies [7,8,10,12,14,15] from various settings around the world. At hotter temperatures, the impact of a fixed glucose load may be greater due to reduced circulating plasma volume, leading to increased diagnoses of GDM.…”

“…In addition to risk associated with individuals, however, there may also be factors in the general environment that influence the likelihood of GDM. Several recent reports suggest that GDM incidence varies with season in diverse settings including southern Europe [7][8][9], Brazil [10], Australia [11][12][13] and Canada [14,15]. These studies show that postload glucose values and incidence of GDM increase at higher ambient temperatures [7,8,10,13,14].…”

“…In the present study, we aimed to explore the association between time of year and GDM diagnosis in a cooler climate with less annual variation than many settings previously studied [7,11,13,14]. In Cambridge, UK, the average annual daily temperature is 11.2°C, with average monthly maximum temperatures between 7.3°C (January) and 22.8°C (July) [16].…”

Temporal Trends without Seasonal Effects on Gestational Diabetes Incidence Relate to Reductions in Indices of Insulin Secretion: The Cambridge Baby Growth Study

“…9 Therefore another factor that could explain at least part of the increased incidence of GDM is exposure to raised or rising ambient temperatures in certain populations. [10][11][12] Following this some studies have reported seasonal variations in the incidence of GDM [13][14][15][16][17] , although this has not been observed in all populations or climates. 18,19 In this study we investigated whether there were temporal and seasonal trends in GDM incidence in our single centre population from Cambridge, U.K. which recruited pregnant women between 2001 and 2009.…”

Brown adipose tissue and glucose homeostasis – the link between climate change and the global rise in obesity and diabetes

“…1,2 This has been observed across the general population in the USA 3 and, in pregnant women in Canada relative to the onset of gestational diabetes. 4 Moreover, the prevalence of gestational diabetes in Canada is higher in the summer and rising ambient temperatures in the 3-4 weeks prior to third trimester glucose tolerance testing can predict gestational diabetes onset. 5 Consequently as brown fat is highly sensitive to changes in ambient temperature and is normally activated by cold exposure it would be expected to become less active as temperature rises.…”