Night owls have higher risk of diabetes and heart disease, study finds

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If you prefer to go to bed and get up later, a sleep chronotype known as a night owl, you may have a higher risk of type 2 diabetes and heart disease, according to a new study.

The night owls were more sedentary, had lower aerobic levels and burned less fat at rest and while active than the first birds in the study. Night owls were also more likely to be insulin resistant, meaning their muscles needed more insulin to get the energy they need, according to the study published Monday in the journal Experimental Physiology.

“Insulin tells the muscles to be a sponge and soak up the glucose in the blood,” said lead study author Steven Malin, an associate professor in the department of kinesiology and health. at Rutgers University in New Jersey.

“Think of it like water from a faucet: you turn on the water and a drop hits the sponge and is immediately absorbed,” Malin said. “But if you’re not exercising, engaging those muscles, it’s like that sponge has to sit for a couple of days and get hard. A drop of water isn’t going to soften it back up.”

If sleep chronotype is affecting how our bodies use insulin and affecting metabolism, then being a night owl could be useful in predicting a person’s risk of heart disease and type 2 diabetes, Malin added.

“The study adds to what we know,” said Dr. Phyllis Zee, director of the Center for Circadian and Sleep Medicine at Northwestern University Feinberg School of Medicine in Chicago, who was not involved in the research.

“There is good evidence that sleeping late has been linked to an increased risk of metabolic and cardiovascular disease,” said Zee, who is also a professor of neurology. “Several mechanisms have been proposed: sleep loss, circadian misalignment, eating later in the day, and being exposed to less morning light and more evening light, which have been shown to affect insulin sensitivity.”

All humans have a circadian rhythm: a 24-hour internal body clock that regulates the release of the hormone melatonin to promote sleep and stops producing it when we wake up. Our body clock also tells us when we’re hungry, when we’re feeling sluggish, and when we feel energized enough to exercise, among many other bodily functions.

Traditionally, sunrise and nightfall regulated the human sleep-wake cycle. Daylight enters the eyes, travels to the brain and activates a signal that suppresses melatonin production. When the sun goes down, the body clock reactivates the production of melatonin and a few hours later sleep comes.

Your personal sleep chronotype, which is believed to be inherited, can disrupt this natural rhythm. If you’re an innate early bird, your circadian rhythm releases melatonin much earlier than normal, encouraging you to be more active in the morning. In night owls, however, the internal body clock secretes melatonin much later, making the early morning hours sluggish and driving peak activity and alertness later in the afternoon and evening.

According to experts, sleep chronotype can have profound effects on productivity, school performance, social functioning and lifestyle habits. Early birds tend to do better in school and are more active throughout the day, which may partly explain why studies have found they have a lower risk of cardiovascular disease, Malin said.

Nocturnal types may take more risks, consume more tobacco, alcohol and caffeine, and are more likely to skip breakfast and eat more later in the day. In addition, research suggests that “later chronotypes have more body fat located more in the stomach or abdominal region, an area that many health professionals believe is worse for our health,” Malin said.

The researchers classified 51 adults without heart disease or diabetes into morning or night time chronotypes, based on their natural sleep and wakefulness preferences. During the study, participants ate a controlled diet and fasted overnight while their activity levels were monitored for a week.

The research team determined that each person’s body mass, body composition and fitness level, and measured levels of insulin sensitivity. In addition, the researchers looked at how each person’s metabolism got most of their energy, whether from fat or carbohydrates.

“Fat metabolism is important because we think that if you can burn fat for energy, that will help the muscle take up glucose in a more sustainable way,” Malin said.

Burning fat can promote endurance and more physical and mental activity throughout the day. Carbohydrates, on the other hand, are what the body uses for intense physical activity. Carbohydrates burn faster, which is why many athletes carb load before a race or marathon.

The test results showed that the early birds used more fat for energy both at rest and during exercise than the night owls in the study, which used more carbohydrates as a fuel source.

More research is needed, Malin said, to confirm the findings and determine whether the metabolic differences are due to chronotype or a possible misalignment between a night owl’s natural preference and the need to wake up early due to hours established by society. work and school

People who are continually out of sync with their innate body clock are said to be in “social jet lag.”

“This extends beyond diabetes or just heart disease,” Malin said. “It can point to a larger societal problem. How are we helping people who may be out of alignment? Are we as a society forcing people to behave in ways that could be putting them at risk?

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