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. 2017 May 15;189(19):E682-E689.
doi: 10.1503/cmaj.160839.

Influence of Environmental Temperature on Risk of Gestational Diabetes

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Free PMC article

Influence of Environmental Temperature on Risk of Gestational Diabetes

Gillian L Booth et al. CMAJ. .
Free PMC article

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.

Methods: We identified all births in the Greater Toronto Area from 2002 to 2014 using administrative health databases. Generalized estimating equations were used to examine the relation between the mean 30-day outdoor air temperature before the time of gestational diabetes mellitus screening and the likelihood of diagnosis of gestational diabetes mellitus 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. Prevalence of gestational diabetes mellitus was 4.6% among women exposed to extremely cold mean outdoor air temperatures (≤ -10°C) in the 30-day period before screening and increased to 7.7% among those exposed to hot mean 30-day temperatures (≥ 24°C). Each 10°C increase in mean 30-day temperature was associated with a 1.06 (95% confidence interval [CI] 1.04-1.07) times higher odds of gestational diabetes mellitus, after adjusting for maternal age, parity, neighbourhood income quintile, world region and year. A similar effect was seen for each 10°C rise in outdoor air temperature difference between 2 consecutive pregnancies for the same woman (adjusted odds ratio 1.06, 95% CI 1.03-1.08).

Interpretation: In our setting, there was a direct relation between outdoor air temperature and the likelihood of gestational diabetes mellitus. Future climate patterns may substantially affect global variations in the prevalence of diabetes, which also has important implications for the prevention and treatment of gestational diabetes mellitus.

Conflict of interest statement

Competing interests: None declared.

Figures

Figure 1:
Figure 1:
Creation of the study cohort.*Restricted to urban and suburban areas in Toronto and surrounding communities (Burlington, Oakville, Mississauga, Brampton, Richmond Hill, Vaughan, Markham, Pickering, Ajax, Whitby and Oshawa). †Among women who immigrated to Canada in 1985 or later. Values in brackets reflect the no. of women who gave birth. OHIP = Ontario Health Insurance Plan.
Figure 2:
Figure 2:
Mean daily outdoor air temperature over the 30-day period before screening for gestational diabetes mellitus (GDM) and corresponding crude prevalence (95% confidence interval [vertical bars]) of GDM. Data are shown for pregnancies (n = 555 911) that occurred in the Greater Toronto Area in Ontario, from 2002 to 2014. Crude and age-adjusted prevalences for GDM per 1°C rise in 30-day mean temperature were highly correlated (R2 = 0.997). Coldest (blue) to moderate (green) to hottest (red) temperatures are shown on the solid line. CI = confidence interval.
Figure 3:
Figure 3:
Relative odds of gestational diabetes mellitus (GDM; unadjusted [black squares] and adjusted [red circles] odds ratios [95% CI]) per 10°C increase in mean daily outdoor air temperature over a 30-day period before screening for GDM. The top 2 models (green text) include all pregnancies, by the 30-day period before 27 weeks gestation and the 30-day period before the actual date of screening, adjusted for maternal age, parity, income quintile, world region and year. The middle 2 models (blue text) include only women with 2 consecutive pregnancies, adjusted for maternal age and parity for each pregnancy. The bottom model (orange text) includes only the subgroup of women with serum glucose results for the 50-g glucose challenge test, adjusted for maternal age, parity, income quintile, world region and year. CI = confidence interval, OR = odds ratio.

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