Pregnant women should dim light 3 hours before bed to reduce diabetes risk, new study says

Pregnant women should dim their home lights and turn off — or at least dim their screens (television, computer monitors and smartphones) — a few hours before bedtime to reduce the risk of gestational diabetes. That’s what recommends a new study by Northwestern Medicine researchers published on Friday in the American Journal of Obstetrics and Gynecology Maternal Fetal Medicine.

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The work shows that pregnant women who are exposed to higher levels of light in the three hours before bedtime appear to be more likely to develop diabetes during pregnancy.

Gestational diabetes is defined as diabetes diagnosed in the second or third trimester of pregnancy. This is the most frequent metabolic problem in pregnancy. Population studies carried out in recent decades show that the world average prevalence of this condition is 16.2%. It is estimated that one in six births occurs in women with some form of hyperglycemia during pregnancy, and 84% of these cases would be due to gestational diabetes.

“Our study suggests that exposure to light before bedtime may be an under-known but easily modifiable risk factor for gestational diabetes,” says lead author Minjee Kim, assistant professor of neurology at Northwestern University Feinberg School of Medicine. and a neurologist at Northwestern Medicine, in a statement.

Exposure to light at night is thought to suppress levels of a hormone called melatonin, disrupt the body’s internal clock, and affect various metabolic processes, such as the regulation of blood sugar levels.

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

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

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The researchers divided the participants into three equally sized groups based on their median exposure to dim light in the three hours before bedtime. The results reveal that 16 of the 247 women who spent only about 1.7 hours (equivalent to 102 minutes) in the dark developed gestational diabetes, compared with 12 of those who spent about 2.2 hours (132 minutes) in the dark and three those who spent about 2.6 hours (156 minutes) in the dark.

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

“Women who spent less time in dim light were five times more likely to develop gestational diabetes compared to those who spent more time in dim light”, points out 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 the participants were exposed to during the day. However, the study has limitations, including the fact that light measurements were only taken for one week.

The good news, points out Kim, is that it was relatively easy to act to reduce that risk.

“Three hours before bed try to dim the lights whenever possible,” recommends the researcher, adding that this also applies to light-emitting devices such as phones. “Try to put them away if possible, but if not, at least try dimming the screen or putting them in night mode.”