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Sleeping in a room exposed to outdoor artificial light at night may increase the risk of developing diabetes, according to a study of nearly 100,000 Chinese adults.

According to the study published Tuesday in the journal Diabetologia, people who lived in areas of China with high light pollution at night were about 28% more likely to develop diabetes than people who lived in less polluted areas.

Ultimately, more than 9 million cases of diabetes among Chinese adults aged 18 and older could be due to outdoor light pollution at night, the authors said, adding that the number is likely to rise as that more and more people are moving to cities.

However, a lack of darkness affects more than urban areas. Urban light pollution is so prevalent that it can affect suburbs and forest parks that can be tens or even hundreds of miles from the light source, the authors said.

“The study confirms previous research on the potential adverse effects of light at night on metabolic function and diabetes risk,” said Dr. Phyllis Zee, director of the Center for Circadian and Sleep Medicine at Northwestern University Feinberg School. of Medicine in Chicago, who did not participate in the study

Previous research has shown an association between artificial light at night and weight gain and obesitydisturbances in metabolic function, insulin secretion and the development of diabetesand cardiovascular risk factors.

A study released earlier this year by Zee and his team examined the role of light in the sleep of healthy adults in their twenties. Sleeping for just one night with dim lighting, like a TV with the sound turned off, increased youth blood sugar and heart rate during the sleep lab experiment.

An elevated heart rate at night has been shown in previous studies be a risk factor for future heart disease and premature death, while higher blood sugar is a sign of insulin resistance, which can ultimately lead to type 2 diabetes.

“Healthy sleep is extremely important in preventing the development of diabetes,” said Dr Gareth Nye, senior lecturer in physiology at the University of Chester in the UK. He did not participate in the Diabetologia study.

“Studies have suggested that inconsistent sleep patterns are linked to an increased risk of type 2 diabetes,” he said in a statement.

The new study used data from the 2010 China Non-Communicable Disease Surveillance Study, which surveyed representative samples of the Chinese population on social demographics, lifestyle factors, and medical and family history. . Blood samples were taken and compared to satellite images of light levels in the area of ​​China each person lived in.

The analysis found that chronic exposure to light pollution at night increased blood sugar levels and led to a higher risk of insulin resistance and diabetes.

However, any direct link between diabetes and nighttime light pollution is still unclear, as living in an urban area is itself a known contributor to the development of diabetes, Nye explained.

“We have known for a long time that living in (a) The urbanized area increases your risk of obesity through increased access to high-fat, ready-to-eat foods, lower levels of physical activity due to transport links, and fewer social activities,” Nye wrote.

Strategies for reducing light levels at night include positioning your bed away from windows and using light-blocking blinds. If low light levels persist, try a sleep mask to protect your eyes.

Be aware of the type of light you have in your bedroom and banish all blue spectrum lights, such as those emitted by electronic devices like TVs, smartphones, tablets and laptops – blue light is the type of most stimulating light,” said Zee.

“If you must have a light on for safety reasons, change the color. You want to choose lights that have more reddish or brownish tones,” she said. If a nightlight is needed, keep it low and level with the floor, so it’s more reflective rather than next to your eye at bed level, she suggested.

Avoid sleeping with the TV on — if you tend to fall asleep while it’s still on, put it on a timer, Zee suggested.

Dim ambient lights at night at least two to three hours before bedtime, and if you “absolutely must use a computer or other light-emitting screens, change the wavelength of the screen light to longer orange-amber ones,” Zee said. “Important, get light during the day – daylight is healthy!”