Background — Cold-induced thermogenesis is known to improve insulin sensitivity, which may be 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 (GDM).
Methods — We identified all births in the Greater Toronto Area in 2002–2014 using administrative health databases. Generalized estimating equations were used to examine the relation between the mean 30-day air temperature prior to the time of GDM screening and the likelihood of GDM diagnosis based on a validated algorithm using hospital records and physician service claims.
Results — Over the 12-year period, there were 555,911 births among 396,828 women. The prevalence of GDM was 4.6% among women exposed to extremely cold mean temperatures (≤-10◦ Celsius) in the 30-day period prior to screening and increased to 7.7% among those exposed to hot mean 30-day temperatures (≥ 24◦ Celsius). Each 10◦ Celsius increase in mean 30-day temperature was associated with a 1.06 (95% confidence interval [CI] 1.04 to 1.07) times higher odds of GDM, upon adjusting for maternal age, parity, neighbourhood income 56 quintile, world region and year. A similar effect was seen for each 10◦ Celsius rise in the temperature difference between two consecutive pregnancies within the same woman (adjusted odds ratio 1.06, 95% CI 1.03 to 1.08).
Interpretation — In our setting, there was a direct relation between outdoor air temperature and the likelihood of GDM. Future climate patterns may significantly impact global variations in diabetes prevalence, which also has important implications for the prevention and treatment of GDM.
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