Diabetes: How much does risk increase for those who sleep in bright light at night?

Scientists in Australia warn that exposure to bright light at night can significantly increase the risk of developing type 2 diabetes.

In a large-scale study, they found that The most critical time is the period from 12:30 after midnight to 6 am. In fact, the greater the exposure to bright light during this period, the greater the risk.

Type 2 diabetes is a chronic condition that affects how the body uses insulin, say scientists from Flinders University in Adelaide. The disease develops gradually over time. It is difficult to treat and is usually associated with a sedentary lifestyle and obesity.

The new study suggests that light intensity at night may be another contributing factor, says the study's leader, an assistant professor of medicine and public health at the university. The results were published in the medical journal The Lancet Regional Health-Europe.

The researchers studied data from 84,790 volunteers whose average age was 62 years. 58% of them were women. None of them had type 2 diabetes at the start of the study. For a week, volunteers wore recorders on their wrists that recorded their exposure to light during the day and at night. The scientists then followed them for 9 years to see whether and how many would develop type 2 diabetes.

By the end of the observation period, 1,997 cases of type 2 diabetes had been registered. The data showed that, compared with volunteers who were virtually unexposed to light at night, those who slept in bright light had an increased risk of developing the disease. Thus, the risk increased from 29% in those who were exposed to bright light in moderate amounts to 53% in those who were exposed to high amounts.

As the expert explains, exposure to light at night disrupts the body's biological clock, the circadian rhythm. This leads to changes in insulin secretion and glucose metabolism. Insulin is a hormone that breaks down glucose (i.e. sugar). Changes in insulin secretion and glucose metabolism affect sugar regulation. In the long term, this can lead to the development of type 2 diabetes.

The study also found that increased light exposure between 0:30 a.m. and 6 a.m. is most unfavorable. This was true regardless of light levels during the day, which regulate the body's biological clock. The association of type 2 diabetes with nighttime lighting persisted even when the researchers controlled for other diabetes risk factors, including:

• Lifestyle
• Sleep habits
• Working hours (shift work makes the situation worse)
• Diet
• Mental health.

“The association between diabetes and bright night light is dose-dependent.– the expert emphasizes. – This finding suggests that reducing exposure to light at night may be a cheap and easy way to prevent or delay the onset of diabetes.”

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