Hotter Temperatures Linked to Increased Risk of Gestational Diabetes

As the weather heats up, the risk of gestational diabetes in pregnant women may rise along with the temperature, according to findings from a study in the Canadian Medical Association Journal.

The link between weather patterns and health outcomes like respiratory exacerbations or infections has been well-studied, but emerging research has begun to suggest that colder temperatures can result in improved insulin sensitivity caused by an increase in brown adipose tissue activity. The recently published study assessed whether outdoor temperatures are associated with the risk of gestational diabetes, a diabetic condition that can arise in pregnancy when placental hormones trigger insulin resistance, putting mother and baby at risk.

Researchers used administrative health databases to identify 555,911 births to nearly 400,000 women in the greater Toronto area who gave birth between April 2002 and March 2014 and did not have diabetes prior to pregnancy. The main exposure variable was the mean outdoor temperature in the 30 days before a woman’s 27th week of pregnancy, when most expecting mothers are screened for gestational diabetes. The study noted that temperatures can vary widely in this geographic area, which tends to have cold winters and hot summers.

According to claims data, gestational diabetes was diagnosed in 6.5% of the pregnancies during the study period. The researchers found that each 10°C (50°F) increase in mean 30-day air temperature was associated with 1.06 times greater odds of gestational diabetes, adjusted for maternal age, world region of origin, neighborhood income level, and other factors. Among the women who had been exposed to a mean 30-day temperature of —10°C (14°F) or lower, the prevalence of gestational diabetes was 4.6%, while it was 7.7% among those exposed to a mean 30-day temperature of 24°C (75.2°F) or higher.

The association between temperature and gestational diabetes was unchanged when analyses were conducted on women with 2 pregnancies in the study period. Interestingly, the positive association persisted regardless of a woman’s region of origin, but women born in hotter-climate countries had about 4% higher rates of gestational diabetes compared with women born in less hot countries.

The researchers noted that their findings could have important implications for preventing gestational diabetes, which occurs in more than 15 million pregnancies worldwide each year.

“If the association between air temperature and risk of gestational diabetes mellitus is real, then modifying the thermal environment (eg, lowering the setting on a home thermostat or spending more time outdoors in cooler weather) may reduce risk of gestational diabetes mellitus,” they wrote.

However, the study results could also be viewed in the broader context of climate change, as projections estimate the temperature of the Earth’s surface will increase by 1°C to 2°C by the year 2050, which could have global health consequences.

“Although changes in temperature of this size may lead to a small relative increase in the risk of gestational diabetes mellitus, the absolute number of women affected in Canada and elsewhere may be substantial,” the researchers concluded.