December 8, 2023

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Does sleeping with lights cause diabetes and obesity?

Does sleeping with lights cause diabetes and obesity?


Does sleeping with lights cause diabetes and obesity?

PNAS: Sleeping with lights on is bad for heart health, increases insulin resistance, and promotes obesity.


Close the doors and windows, close the curtains, and turn off all the lights. This should be a routine step for most people before going to bed, but many people like to sleep with the lights on for various reasons.


Previous research has shown that light during the day increases heart rate by activating the sympathetic nervous system, which keeps the heart racing at high speed and increases alertness for the challenges of the day.


So, does lighting during sleep at night have a similar effect?


On March 14, 2022, a research team from Northwestern University Feinberg School of Medicine published in the Proceedings of the National Academy of Sciences (PNAS) titled : Light exposure during sleep impairs cardiometabolic function function) research paper [1] .


The findings suggest that just one night of exposure to moderate room light during sleep impairs blood sugar and cardiovascular regulation, thereby increasing the risk of heart disease, diabetes and metabolic syndrome . This reminds us that it is very important to avoid or minimize the amount of light during sleep at night.


Does sleeping with lights cause diabetes and obesity?




Light increases heart rate, and the body cannot rest


In this study, the research team found that when a person sleeps in a well-lit room, his heart rate increases, and even when asleep, the autonomic nervous system (divided into the sympathetic and parasympathetic nervous systems) also will be activated.

This is a bad situation because normally a person’s heart rate and other cardiovascular system parameters decrease at night and increase during the day.

The sympathetic and parasympathetic nervous systems regulate our daytime and nighttime physiology.

The sympathetic nervous system is responsible for daytime regulation, while the parasympathetic nervous system is responsible for nighttime regulation.

Light during nighttime sleep increases the activation of the sympathetic nervous system, preventing the body from resting effectively.




Does light during sleep cause diabetes and obesity?


As early as 2019, the National Institutes of Health published a large-scale study in JAMA Internal Medicine [ 2] .

This five-year follow-up survey of 43,222 women found that turning on the lights at night Sleeping can lead to obesity in women, and turning off the lights before going to bed can reduce the risk of obesity in women.


Does sleeping with lights cause diabetes and obesity?


What is the reason behind this?


The study, published in PNAS , shows that people sleeping in a room with lights on can develop insulin resistance the next day , which is when cells in tissues and organs such as muscle, fat and liver do not respond well to insulin and fail to Uses glucose in the blood for energy.

To compensate for this, the pancreas produces more insulin to keep blood sugar stable, and over time, blood sugar rises, and insulin resistance predisposes to metabolic syndrome and type 2 diabetes .


Does sleeping with lights cause diabetes and obesity?



The new study explains the specific mechanism by which sleeping with lights on at night can lead to obesity, discovered in a JAMA Internal Medicine paper, suggesting that lights during nighttime sleep are affecting the body’s ability to regulate glucose.

The research team said that when you turn on the lights to sleep at night, you may not feel any difference, but your brain will feel that it is difficult for you to enter a deep sleep under the light, and the sleep duration is poor, and it is easy to wake up halfway. Come, that is, the body cannot rest as well as it should.




This is not uncommon

It is not uncommon to be exposed to artificial light during sleep at night, whether it is from indoor lighting equipment or from outdoor light sources, especially in big cities, outdoor light pollution is very serious, according to statistics, up to 40% of people are sleeping bedside lights or bedroom lights and/or TVs are on.


Light during the day is an important factor in health, but at night, light is no longer beneficial and can damage heart and endocrine health.


In the new study, the research team tested 20 participants (10 people in each group ) sleeping under 100 lux light (moderate light intensity, the effect of turning on the lights in a normal bedroom at night) and 3 lux light (low light) for one night.

The results showed that moderate light intensity puts the body into a state of alert, in which the heart rate increases, the force of the heart’s contractions increases, and blood is transported to the blood vessels faster for oxygenated blood flow.


Does sleeping with lights cause diabetes and obesity?




Recommendations from the research team


Phyllis Zee , the study’s corresponding author, gives three suggestions for reducing light during nighttime sleep:

1) Don’t turn on the light , if you have to turn on the light (older people may do it for safety), set it to a dim light closer to the floor;

2) Color is important , amber or red/orange light is less stimulating to the brain, do not use white or blue light, and keep it away from sleeping people;

3) If the outdoor light cannot be controlled, an eye mask is a good choice , or adjust the position of the bed so that the outdoor light does not directly shine on the face.



Seeing this, many people may have a question, is their room too bright? What kind of light intensity is high during sleep at night? Corresponding author Phyllis Zee said that as long as this light allows you to see, it is already too bright. He also said the findings are very important for people living in modern society, where light pollution is now very high, both outdoors and indoors. This reminds us that it is very important to avoid or minimize the amount of light during sleep at night.




Reference :

Does sleeping with lights cause diabetes and obesity?

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Important Note: The information provided is for informational purposes only and should not be considered as medical advice.