Sleeping With Lights On May Raise Blood Sugar Levels

Some people feel more comfortable sleeping with the lights on. However, exposure to light while sleeping can negatively affect health, including by increasing heart rate and elevating blood glucose levels in the body.

A study conducted by researchers from Northwestern University in Chicago found that exposure to artificial light at night can increase heart rate during sleep and impair glucose metabolism the following morning.

The light exposure was found to impair glucose and cardiovascular regulation, thereby increasing risk factors for heart disease, diabetes, and metabolic syndrome.

In the study, scientists recruited 20 young adults to stay in a laboratory for three days and two nights. A week before the study, researchers measured the participants' sleep habits using actigraphy and sleep diaries. The participants were then randomly assigned to sleep under one of two conditions: dim room light or bright room light.

As reported by Medical News Today, the researchers found that exposure to high room lighting increased heart rate during sleep and led to higher insulin resistance the next morning.

Corresponding author Phyllis C. Zee stated that the increase in heart rate and insulin levels when sleeping with lights on may be caused by arousal during sleep. Additionally, light can affect the circadian clock and alter melatonin secretion.

"[We hypothesize] that light activates brain regions that regulate the autonomic nervous system because there is a link between changes in heart variability and insulin resistance," she explained.

Another study conducted in 2019 also found that artificial light at night, such as from night lights or televisions, was linked to obesity in women. These findings indicate that light exposure during sleep adversely impacts metabolic regulation.

The researchers concluded that avoiding artificial light during sleep can benefit cardiometabolic health.