What happens when you don’t get enough sleep? Blood samples show cardiac risks.

Reducing sleep on a regular basis can damage immune stem cells, potentially increasing the risk of inflammatory disorders and heart disease, a small new study suggests.

An analysis of blood samples from 14 healthy volunteers who agreed to shorten their sleep by 1.5 hours each night for six weeks revealed long-term changes in the behavior of these stem cells, which led to a proliferation of white blood cells which can cause inflammation. , according to the report published Wednesday in the Journal of Experimental Medicine.

“The key message from this study is that sleep decreases inflammation and sleep loss increases inflammation,” said study co-author Filip Swirski, director of the Icahn Institute for Cardiovascular Research at Mount Sinai in New York. “In subjects who had undergone sleep restrictions, the number of immune cells circulating in the blood was greater. These cells are key players in inflammation.”

While a certain amount of inflammation is needed to fight infection and heal wounds, too much can be harmful, he explained. Excessive and persistent inflammation has been linked to heart disease and neurodegenerative diseases, such as Alzheimer’s, he added.

To see the impact of restricted sleep on the immune system, Swirski and his colleagues conducted experiments in humans and mice.

For the human study, the researchers recruited volunteers (seven men and seven women with an average age of 35) who typically slept eight hours a night.

In the first part of this experiment, the volunteers were monitored sleeping as they normally did for six weeks, after which the researchers took blood samples and analyzed the content of immune cells. For the next phase, the volunteers’ sleep was reduced by 90 minutes each night for six weeks. Once again, the researchers took blood samples and totaled the number of immune cells.

When Swirski and his colleagues compared the data from the two sets of blood samples, they found an increase in the number of immune cells after the six weeks of sleep restriction. A previous animal study had revealed an increase in inflammation when the number of immune cells increased.

In addition, the stem cells that give birth to immune cells had changed as a result of the six weeks of shortened sleep. Although their basic DNA coding remained the same, the programming that controls which bits of genetic material would be turned on and off was altered, a process known as epigenetics.

Although the number of immune cells may return to normal weeks later, there appears to be a more permanent mark on the stem cells. Like scars on the body that can grow with repeated injuries, the marks can spread if there are more episodes of restricted sleep, Swirski said.

These marks on stem cells, through a series of steps, ultimately lead to less diversity among immune cells. Less diversity means that some jobs go unfilled while others become redundant, Swirski explained. So the immune system works less well, in some ways the way building a house wouldn’t be as successful if the construction crew had carpenters but no plumbers.

How lack of sleep affects our age

The changes the Mount Sinai researchers saw in the experiments mirror what happens as humans age.

“As a natural consequence of aging, we lose diversity,” Swirski said. “By interrupting sleep, we are accelerating the aging process.”

“The real key is that there are things we can do with lifestyle — getting enough sleep, managing stress, getting enough exercise, eating a healthy diet — that can slow down biological aging,” he said. Swirski. “We may not live forever, but we can live into old age while maintaining the quality of our lives by paying attention to some of these lifestyle factors.”

Although it was known from clinical observations that chronic lack of sleep could weaken the immune system, the new study provides a mechanism to explain how it happens, said Dr. Stephen Chan, director of the Institute of Vascular Medicine at the University of Pittsburgh School of Medicine. .

This goes to show that you can’t run yourself a wreck during the week and make up for it on the weekend.

— Kristen Knutson, Northwestern Feinberg School of Medicine

“We fundamentally didn’t understand why, at the cellular level, sleep was so important in controlling the immune system,” he said. “It is very important to understand how sleep can affect inflammatory diseases such as sepsis, cardiovascular disease, Alzheimer’s and dementia.”

Scientists hoped that it would be possible to catch up with bad sleep and return to normal.

“It turns out that’s not true,” Chan said. “We knew there was a connection between sleep and the development of dementia years later. This could be the explanation.”

He hopes more studies will examine whether the impact of poor sleep habits is permanent.

“This study deserves a lot of follow-up on the durability of the effects,” Chan said. “Will they last for years, decades, or just months?”

The new study is “elegant,” said Kristen Knutson, an associate professor at the Center for Circadian and Sleep Medicine at Northwestern Feinberg School of Medicine.

“They emphasized the long-term effects of sleep impairment that we don’t recover from quickly, and they showed that in both animal and human studies,” he said. “It just goes to show that you can’t run yourself a wreck during the week and make up for it on the weekend.”

When you say immune system, people only think of infectious diseases, Knutson said.

“But it plays an important role in many other health conditions,” he added. “Anything that impairs the immune system can have far-reaching effects.”

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