Do you leave the blinds up at night or sleep with the bedside lamp on? If so, it could have a negative impact on health.
Researchers at Northwestern University in Illinois (USA) have discovered that even little light during sleep can damage the cardiovascular system and metabolism. The reason for this: when it is bright, the heart rate increases and the body cannot recover properly.
Laboratory study with 20 participants
A total of 20 young, healthy adults took part in the parallel group study. First, the subjects slept one night in low, dimmed light (below 3 lux). They spent the following night under the influence of moderate light (100 lux) from above.
Both the heart rate during the night and the insulin resistance the next morning were measured. The scientists found that the nocturnal heart rate was increased in the study participants who slept in a light intensity of 100 lux. Likewise their insulin resistance the next morning.1
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The influence of light on the body
The fact that light has a decisive influence on our body and our «internal clock» is nothing new. In daylight, the vegetative nervous system is activated and the heart rate increases. At night, when it is dark, the body goes into a kind of resting mode. The circadian rhythm also affects the release of hormones and blood pressure.2
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As the scientists found, light during sleep can produce a similar effect on the nervous system as the influence of light during the day. Exposure to light causes the body to go on alert. In this condition, the heart rate increases, as does the speed at which blood flows through the body. As a result, the body cannot rest and regenerate properly. A condition that is still noticeable the next day – for example through increased insulin resistance.
health effects
As early as 2018, it was found that even a single night of exposure to light while sleeping can lead to increased insulin resistance the next morning. With insulin resistance, the body is no longer able to use glucose from the blood for energy production. To compensate, the pancreas produces more insulin. The blood sugar level rises. In the long term, this can lead to the development of type 2 diabetes.3
Study author Dr. Phyllis Zee, director of sleep medicine at Northwestern University’s Feinberg School of Medicine, said in a university statement, «The results of this study show that just a single night of moderate room lighting during sleep improves glucose and cardiovascular regulation can affect what are risk factors for heart disease, diabetes and metabolic syndrome.” She therefore emphasizes: “It is important for people to avoid or minimize exposure to light during sleep.”4
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Tips to avoid exposure to light while sleeping
Artificial light sources are making it increasingly difficult for us in our modern society to stay away from disturbing light sources at night and to maintain the natural day-night rhythm. dr Phyllis Zee therefore recommends:
- Don’t turn on the lights at night. If light is required, the source should be as weak as possible and close to the ground.
- Red and orange light are less stimulating to the brain. White or blue light should therefore not be used.
- Eye masks and blackout curtains can help you get a restful sleep despite external light sources. The orientation of the bed can also be a deciding factor.