Pregnant women were advised to try to put their phones away in the hours before bed.

Pregnant women advised to dim lights before bed to reduce diabetes risk

Those exposed to more light in hours before sleep appear more likely to develop gestational diabetes, researchers suggest

While reading until the small hours or scrolling under the covers are common bedtime habits, pregnant women might want to switch off sooner to reduce their risk of developing gestational diabetes, researchers have suggested.

According to the Royal College of Obstetricians and Gynaecologists, gestational diabetes affects at least four to five in 100 women during pregnancy. If it is not well controlled it can lead to complications, including health problems for the baby.

Now research published in the American Journal of Obstetrics and Gynecology Maternal Fetal Medicine has revealed pregnant women who are exposed to greater levels of light in the three hours before sleep appear to be more likely to develop diabetes during their pregnancy.

“Light at night may be an unrecognised risk for acquiring a serious pregnancy complication,” said Dr Minjee Kim, the lead author of the study at Northwestern University.

Pre-diabetes study finds benefit in brighter days and dimmer evenings

Among other studies, researchers have previously found people who work shifts are at greater risk of type 2 diabetes, while greater exposure to outdoor artificial light at night has also been linked to an increased risk of the condition.

It is thought exposure to light at night suppresses levels of a hormone called melatonin, disrupts the body’s internal clock, and impacts various metabolic processes, such as regulation of blood sugar levels.

“While we can’t prove it from this observational study, similar mechanisms may play a role in pregnant women,” said Kim.

Between 2011 and 2013, Kim and colleagues asked 741 pregnant women in the US who were in their second trimester to wear light sensors on their wrists and complete a daily sleep diary for around a week.

The researchers split the participants into three even-sized groups based on their median exposure to dim light in the three hours before sleep. The results reveal 16 of the 247 women who only spent about 1.7 hours in dim light developed gestational diabetes, compared with 12 of those who spent about 2.2 hours in dim light, and three of those who spent about 2.6 hours in dim light.

While only a small number of women developed gestational diabetes, the results revealed a trend.

“Women who spent the least time in dim light had fivefold greater odds of developing gestational diabetes compared to those who spent the most time in dim light,” said Kim.

The researchers say an association was present even when they took into account factors such as age, sleep quality and duration, body mass index and how much light participants were exposed to during the day.

However the study does have limitations, including that the light measurements were made only over one week.

The good news, Kim said, was that it was relatively easy to take action. “Starting three hours before bedtime, try to dim the lights whenever possible,” Kim said, adding that also applied to light-emitting devices such as phones. “Try to put them away if possible, but if not, at least try to dim the screen or put them on the night mode.”

Dr Faye Riley, a research communications manager at Diabetes UK, said: “The study hints at a link between artificial light exposure before sleep and increased risk of gestational diabetes but we’ve a lot more to learn before we can say with any confidence that limiting artificial light exposure could be helpful in the prevention of the condition.

“What we do know is that managing your weight, eating healthily and keeping active before pregnancy can help to reduce your risk of gestational diabetes.”

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