Dimming lights 3 hours before sleep could reduce risk of gestational diabetes: Study

New Delhi: Scientists are advising pregnant people to turn off or dim the lights in their homes a few hours before bedtime to reduce the risk of developing gestational diabetes mellitus.

The lights in question also include those coming from computer monitor and smartphone screens, according to the research from Northwestern Medicine, Northwestern University, US.

Women who developed gestational diabetes mellitus in the multi-site study had greater light exposure in the three hours before sleep onset, the study said.

They did not differ in their light exposure during daytime or sleep or in their activity levels compared to those who did not develop it.

"Our study suggests that light exposure before bedtime may be an under-recognized yet easily modifiable risk factor of gestational diabetes," said lead study author Minjee Kim, assistant professor at Northwestern University.

Growing evidence suggests exposure to light at night before bedtime may be linked to impaired glucose regulation in non-pregnant adults.

Bright light exposure prior to sleep can come from bright lights in your home and from devices like TVs, computers and smartphones.

However, little is known about the effect of evening light exposure during pregnancy on the risk of developing gestational diabetes, a common pregnancy complication with significant health implications for both the mother and the offspring.

The study, believed to be one of the first multi-site studies to examine light exposure before sleep on the risk of developing gestational diabetes, is published in the American Journal of Obstetrics and Gynecology Maternal Fetal Medicine.

"It's alarming," Kim said.

"Gestational diabetes is known to increase obstetric complications, and the mother's risk of diabetes, heart disease and dementia. The offspring also are more likely to have obesity and hypertension as they grow up," Kim said.

Data show that women who have gestational diabetes are nearly 10 times more likely to develop type 2 diabetes mellitus compared to those do not have glucose issues during pregnancy, Kim said.

"We don't think about the potential harm of keeping the environment bright from the moment we wake up until we go to bed," Kim said.

"But it should be pretty dim for several hours before we go to bed. We probably don't need that much light for whatever we do routinely in the evening," Kim said.

Which source of bright light causes the problem is not known yet, but it might all add up, Kim said.

"Try to reduce whatever light is in your environment in those three hours before you go to bed," Kim said.

"It's best not to use your computer or phone during this period. But if you have to use them, keep the screens as dim as possible," Kim said, suggesting people use the night light option and turn off the blue light.

If pregnant persons develop gestational diabetes with the first pregnancy, they are more likely to have it with the next pregnancy.

Pre-sleep light exposure increases heart rate and may lead to abdominal obesity, insulin resistance, increased blood pressure.

Pre-sleep light exposure may also affect glucose metabolism through sympathetic overactivity, meaning the heart rate goes up before bed when it should go down.

"It seems there is inappropriate activation of the fight or flight response when it is time to rest," Kim said.

Data showed the sympathetic overactivity may lead to cardiometabolic disease, which is a cluster of conditions including abdominal obesity, insulin resistance, increased blood pressure and an imbalance of lipids, all leading to cardiovascular disease.

The study of 741 women in their second trimester was conducted at eight clinical US sites between 2011 and 2013. The participants' light exposure was measured by an actigraph worn on their wrists.

The women were measured during the second trimester of pregnancy, the time when they receive routine screening for gestational diabetes.

According to the results, pre-sleep light exposure remained significantly associated with gestational diabetes, after adjusting for various factors.

"Turning down the lights is an easy modification you can make," Kim said.