Sleeping with night lights on is not enough, study: Low light enough to increase risk of heart disease and metabolic disease

Many people like to sleep with a night light, but a study by Northwestern University found that even if it is not very bright, just one night is enough to damage blood sugar and cardiovascular regulation, increasing the risk of heart disease, diabetes and metabolic problems in the future. .

It is difficult to completely avoid light in the sleeping environment at night. Sometimes it is the night light at home. The survey found that up to 40% of the people sleep with the bedside light or bedroom light on, or turn on the TV. Even sleeping with no lights on, it can sometimes be difficult to avoid light sources outside the home, especially in large urban areas.

Scientists at the Center for Circadian Rhythm and Sleep Medicine at Northwestern University Feinberg School of Medicine found that about 5% to 10% of ambient light reaches the eye through closed eyelids. Causes a deficit in slow wave and rapid eye movement sleep, the sleep stages where most cell turnover occurs. These dim lights can also lead to increased heart rate, increased insulin resistance, and imbalances in the sympathetic nerves, which govern fight or flight, and the parasympathetic nervous system, which govern rest and relaxation, and are associated with higher blood pressure in healthy people.

Northwestern University scientists say that light during the day activates the sympathetic nervous system to increase heart rate, put the heart into high gear, and increase alertness to cope with challenges. A similar effect occurs when exposed to light during sleep at night.

The study tested the effects of sleep in participants who were exposed to 100 levels of moderate light and 3 levels of low light overnight, and found that moderate light caused the body to enter a higher state of alertness called sympathetic triggering. In this state, the heart rate will increase, the contractility of the heart will also increase, and the blood delivery speed will also increase, reaching the flow of oxygenated blood.

An elevated heart rate has a big impact. Heart rate and other cardiovascular parameters are typically lower at night and higher during the day, the scientists said. When sleeping in a well-lit room, the heart rate increases, meaning the autonomic nervous system is triggered even when asleep. Numerous studies have found that elevated heart rate at night is a risk factor for future heart disease and premature death.

In addition, insulin resistance occurs the morning after people sleep in a bright room. Insulin resistance is when cells in muscle, fat, and living cells don’t respond well to insulin and can’t use blood glucose for energy, causing the pancreas to produce more insulin, and over time blood sugar rises.

Hyperglycemia is a marker of insulin resistance, which means the body stops using glucose properly, sending the pancreas into overdrive and eventually out of balance. Past research has found that insulin resistance eventually leads to type 2 diabetes. Previous studies have found that many people exposed to light during sleep are overweight or obese, and this study uncovers the underlying mechanism that suggests that light affects the ability to regulate glucose.

The researchers said that in addition to sleep, nutrition and exercise, light during the day is also an important factor affecting health. This study tells us that please try to avoid light at night, even if the environment is not very bright, it is enough to damage the normal functioning of the heart and endocrine. If you have to turn on the lights, the researchers suggest, as long as there is enough light to allow you to see your surroundings clearly, it is too bright.

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