Relationship between environmental temperature and the diagnosis and treatment of gestational diabetes mellitus: An observational retrospective study.

Introduction: Environmental temperature has been described to affect plasma glucose levels after oral glucose tolerance testing (OGTT).

Aims: We evaluated the relationship between seasons and environmental temperature and gestational diabetes mellitus (GDM) diagnosis and treatment.

Methods: We analyzed data from 2374 women retrospectively. GDM was diagnosed in 473 patients by a 100-g OGTT. OGTT results and needing of insulin therapy were evaluated in relation to seasons and environmental temperature (mean temperature and temperature change) the day of the OGTT and the preceding 14 and 28 days.

Results: We found significant seasonal differences in the percentage of GDM: 24.4% in summer vs. 15.6% in autumn (p < 0.01). The odds ratio (OR) for being diagnosed with GDM was 1.78 in summer relative to autumn, after controlling for age. A higher mean temperature the day of the OGTT and the preceding 14 and 28 days increased the risk of being diagnosed with GDM the months in which temperature was rising (March-August) but not the months in which temperature was decreasing (September-February). We observed a negative correlation between temperature and fasting glucose and a positive correlation with post-load glucose. Neither the season nor the environmental temperature affected the risk of requiring insulin therapy.

Conclusions: There is a higher prevalence of GDM diagnosis at warmer seasons and at rising temperatures the 2-4 weeks prior to the OGTT. The impact of temperature is different between fasting and post-load glucose.