The glow of a lightbulb or smartphone at night can mess with the body's circadian rhythm. Even exposure to artificial light at night, whether it be yellow light from your reading lamp or blue light from your smartphone or TV, can make it harder to fall asleep.

Now, a new study suggests that exposure to artificial light after midnight may raise the risk of developing type 2 diabetes.

the study

research was conducted among nearly 85,000 people, between the ages of 40 and 69, who wore devices on their wrists, day and night for one week, to track their exposure to different levels of light.

The health of the cohort was tracked for as long as nine years.

Those volunteers who later went on to develop type 2 diabetes were more likely to have been exposed to light between 12:30 am and 6:00 am, during the week-long study period.

study conclusions

While this study cannot prove the cause-effect connection, they do reveal a relationship between brighter light in the middle of the night and the risk of a metabolic disorder.

Those participants in the top 10 percent for light exposure at night had as much as a 67 percent higher risk of developing type 2 diabetes than those in the bottom 50th percentile.

the researchers conclude:

“Advising people to avoid night light is a simple and cost-effective recommendation that may ease the global health burden of type 2 diabetes.”

One major limitation of the study is that researchers were not able to take into account meal times, which can have an impact on both circadian rhythms and glucose tolerance.

Interestingly, light at night itself can trigger insulin resistance, as another study found. Another experiment suggest that when melatonin is disrupted and the circadian rhythm is thrown out of whack, it can lead to the pancreas secreting less insulin. This could be a contributing factor to the development of diabetes. So those two other factors are also linked.

References:

The study was published in The Lancet Regional Health – Europe. https://www.thelancet.com/journals/lanepe/article/PIIS2666-7762(24)00110-8/fulltext

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