HQ Team
March 13, 2023: Exposure to bright lights before sleep can induce gestational diabetes mellitus in pregnant women, a study by Northwestern Medicine, an affiliate of Northwestern University Feinberg School of Medicine in Chicago, found.
Researchers conducted the study on 741 women in their second trimester at eight clinical U.S. sites between 2011 and 2013.
An actigraph on their wrists measured the participants’ light exposure. The women were measured during the second trimester of pregnancy when they received routine screening for gestational diabetes.
After adjusting for factors such as age, body mass index, ethnicity, employment schedule, sleep regularity index, and daytime light exposure, pre-sleep light exposure remained significantly associated with gestational diabetes, according to the study.
Bright light exposure before sleep can come from bright lights in your home and devices like T.V.s, computers and smartphones.
Impaired glucose regulation
Exposure to light at night before bedtime may cause impaired glucose regulation in non-pregnant adults.
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 mother and offspring.
Pre-sleep light exposure increases heart rate and may lead to abdominal obesity, insulin resistance, and high blood pressure.
Women who developed gestational diabetes mellitus in the multi-site study had greater light exposure three hours before sleep onset. 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 Dr Minjee Kim, assistant professor of neurology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine neurologist.
Lose body weight
The researchers recommended lights be dimmed a few hours before bedtime to reduce the risk of gestational diabetes. They also urged pregnant women to exercise and lose body weight.
Gestational diabetes is on the rise globally and in the U.S.
About 4.5% of first-time pregnant women with a baby born between 2011 and 2013 developed gestational diabetes, which has been increasing on average by 3.4% per three-year period until 2019. In 2020, the rate of gestational diabetes was 7.8% of all births in the U.S.
“It’s alarming,” Kim said. “Gestational diabetes increases obstetric complications and the mother’s risk of diabetes, heart disease and dementia. The offspring also is more likely to have obesity and hypertension as they grow up.”
Pre-sleep light exposure may 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 that women with gestational diabetes are nearly ten times more likely to develop type 2 diabetes mellitus compared to those who do not have glucose issues during pregnancy, Kim said.
Evening light
“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 dim for several hours before bed. We probably don’t need that much light for whatever we do routinely in the evening.”
Scientists don’t know which bright light source causes the problem, but Kim said it might all add up.
“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 must use them, keep the screens as dim as possible,” Kim said. People should use the night light option and turn off the blue light.
If pregnant persons develop gestational diabetes during the first pregnancy, they are likely to have it in the subsequent pregnancy.
Cardiometabolic disease
Data showed that sympathetic overactivity might lead to cardiometabolic disease, a cluster of conditions including abdominal obesity, insulin resistance, increased blood pressure and an imbalance of lipids, all leading to cardiovascular disease.
An increasing body mass index and old age are partially responsible.
“But even after adjusting for BMI and age, gestational diabetes is still rising,” Kim said. “We have a lot to prove, but I worry that the light may silently contribute to this problem without most people realizing the potential harm.”
“Turning down the lights is an easy modification you can make,” Kim said.
“Now I’m the light police at home,” Kim said. “I see all this light I never thought about before. I try to dim the light as much as possible. You don’t need bright light for evening activities such as dinner and bathing the kids.”
