Turning off smartphones and dimming lights close to bedtime could reduce pregnant women’s risk of gestational diabetes, according to US academics.
Gestational diabetes, a form of diabetes which develops in pregnancy, affects around five per cent of women expecting a baby.
Most have normal pregnancies and return to normal after giving birth, but the condition has been linked to premature birth and unusually large babies, and a higher risk of type 2 diabetes for women later in life.
A study now suggests women with greater exposure to light in the three hours before falling asleep have a greater risk of developing gestational diabetes.
Researchers looked at 741 women in their second trimester of pregnancy, whose light exposure was measured for seven consecutive days with a wrist-worn tracker.
US researchers looked at 741 women in their second trimester of pregnancy, whose light exposure was measured for seven consecutive days with a wrist-worn tracker. Scientists split women into three groups, based on how much light above 10 lux they were exposed to
The study set out to see how much of the three hours before bed women spent in normal, brighter light – measuring above the light strength measurement of 10 lux.
The trackers also measured the time they spent in dim light, below 10 lux, which is about the level of candlelight, and can be achieved from a dimmed overhead light or table lamp.
Researchers split women into three groups, based on how much light above 10 lux they were exposed to.
The women exposed to the most normal light, for an average of one hour and 19 minutes in the three hours before bed, were about five-and-a-half times more likely to develop gestational diabetes.
This was compared to the pregnant women who got the least normal light – only about 24 minutes in the three hours before bed.
The study has limitations, as it only captured only a week of women’s exposure to light during pregnancy, which might not have been typical.
There is more evidence linking light exposure to diabetes in people who are not pregnant, so much more evidence is needed.’
But the authors conclude that people should limit the light they are exposed to before bedtime, including from electronic devices.
Dr Minjee Kim, the neurologist who led the study from Northwestern University in the US, 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.
‘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.’
She advised: ‘Try to reduce whatever light is in your environment in those three hours before you go to bed.
‘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.’
Most electronic devices have settings to limit the blue light they emit, which affects melatonin – the hormone which helps the body know when to sleep and wake.
Melatonin is also linked to how well the body regulates blood sugar, which might explain how light late at night could be linked to gestational diabetes in pregnancy.
The study identified a third group of women with moderate exposure to brighter light, who got about 48 minutes of normal, non-dim light in the three hours before bed.
Compared to the group with the least normal light exposure, who got 24 minutes of it, women with moderate exposure were around four times as likely to get gestational diabetes.
In total, 31 women in the group, or around four per cent, developed gestational diabetes in pregnancy.
They did not differ in their light exposure during the daytime, or their exercise level, compared to those who did not develop it.
But, even when factors like their age and weight were taken into account, women’s risk of gestational diabetes was higher if they had higher light exposure before bedtime.
The study is published in the American Journal of Obstetrics and Gynecology Maternal Fetal Medicine.
Dr Kim said: ‘Still regular exercise and eating healthily are among the most important things women can do to limit their risk of gestational diabetes.
‘But turning down the lights is an easy modification you can make as well.’
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