Exposure to artificial light at night may increase the risk of diabetes

We already knew the harmful effects of artificial light, and in particular blue light from screens, on sleep. Published in the journal Diabetologia (Source 1), a new study reveals that nocturnal exposure to artificial outdoor light is associated with an increased risk of diabetes. More precisely, artificial light at night would alter the blood sugar control (blood glucose level), and would thus increase the risk of diabetes.

Recalling that exposure to artificial nocturnal light (AN) is harmful for biodiversity, since it disrupts the biological clock of many animals (birds and insects in particular), the researchers point out that many previous studies have highlighted a effect of LAN on human metabolism. Nocturnal exposure to artificial light could thus increase the risk of overweight or obesity, but also the risk of cardiovascular disease.

Here, the study was conducted using data from a Chinese non-communicable disease surveillance survey. The sample, representative of the Chinese population, comprised 98,658 adults (half of whom were women) with an average age of 42.7. The latter provided information about their medical but also medical and family situations, their way of life and levels of education. The participants’ body mass index (BMI) was calculated, and blood samples were taken to obtain fasting and after-meal blood glucose levels, as well as glycated hemoglobin. The latter corresponds to a form of glucose bound to hemoglobin (protein of red blood cells allowing the transport of oxygen), and allowsassess glycemic control over a long period, in this case 8 to 12 weeks here.

Using satellite data, the researchers assigned each participant an average level of exposure to outdoor artificial light. These levels were ranked from lowest to highest, and grouped into five quintiles (groups of 20%), knowing that the median light intensity in the highest quintile was 69 times higher than in the lowest.

More than 9 million cases of diabetes potentially linked to this exposure

Verdict: The highest quintile of nocturnal artificial light (ANL) exposure was associated with a 28% increase in the prevalence of diabetes compared to lower quintile areas. On average, for every 42 people living in regions with high exposure to LAN (highest quintile), one more case would not have occurred if these people had lived in regions with lower exposure (lowest quintile).

By extrapolating the data, the researchers estimated that more than 9 million cases of diabetes among Chinese adults could thus be attributed to nocturnal exposure to artificial outdoor light. A figure that could well increase due to massive urbanization and the massive rural exodus in China.

The authors of the study call for further studies to be carried out to verify whether this is indeed a causal relationship between the risk of diabetes and exposure to LAN. This would then be considered as a real risk factor for diabetes.

Leave a Comment