Night-time exposure to bright light increases the risk of developing type 2 diabetes, a recent study revealed.

In a large-scale study involving 85,000 healthy adults without diabetes, researchers from the Flinders University, Australia, discovered that exposure to light between 12:30 a.m. and 6 a.m., is linked to a 67% increased risk of developing diabetes.

"Type 2 diabetes risk was higher in people exposed to brighter night light and in people exposed to light patterns that may disrupt circadian rhythms. Avoidance of light at night could be a simple and cost-effective recommendation that mitigates the risk of diabetes, even in those with high genetic risk," the researchers wrote in the study published in the journal The Lancet Regional Health.

The participants were aged between 40 and 69 years at the time of recruitment. Their light exposure was captured by wrist-worn devices, which contained a silicon photodiode light sensor with a peak sensitivity wavelength of 560 nm.

The research team followed up with the participants for about nine years and found that those with the greatest nighttime light exposure faced the highest risk, irrespective of the time they were exposed to light during the day.

"Night light exposure and genetic risk were found to be independent risk factors for developing type 2 diabetes," the researchers wrote.

The researchers attribute the association to the disruption of the body's circadian rhythm which can interfere with several body functioning.

"Light exposure at night can disrupt our circadian rhythms, leading to changes in insulin secretion and glucose metabolism. Changes in insulin secretion and glucose metabolism caused by disrupted circadian rhythms affect the body's ability to regulate blood sugar levels, which can ultimately lead to the development of type 2 diabetes," said Andrew Philips, a senior author of the study.

The study has certain limitations. The researchers could not explore the impact of food timing due to a lack of temporal dietary data. Food timing can affect human circadian rhythms, influencing glucose tolerance and body fat levels, potentially influencing the links between light exposure, circadian disruption, and diabetes. Since the participants in the cohort had an average age of 62.3 ± 7.85 years, it is uncertain whether the findings may apply to younger age groups.

However, based on their findings, the researchers suggest that "reducing your light exposure at night and maintaining a dark environment may be an easy and cheap way to prevent or delay the development of diabetes."

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