A new study has shown that chronic sleep deprivation in a small group of healthy adults increased the production of immune cells linked to inflammation, in addition to altering the DNA of those same cells.
“Not only did the number of immune cells increase, but the activation and programming of these cells might be done in a different way at the end of the six weeks of sleep restriction,” said the co-author of the study, Cameron McAlpine, assistant professor of cardiology. and neuroscience at Mount Sinai Icahn School of Medicine in New York. “Together, these two factors can predispose someone to conditions like cardiovascular disease.”
A certain amount of immune system inflammation is necessary for the body to fight infections and heal wounds, but an overactive immune system can be harmful and lead to an increased risk of autoimmune and chronic diseases, experts say.
The study was published September 21 in the Journal of Experimental Medicine.
“This work is consistent with views in the field that sleep restriction may increase the risk of type 2 diabetes and hypertension,” said Steven Malin, associate professor in Rutgers University’s Department of Kinesiology and Health. in New Jersey.
“Concretely, these results support the idea that we should develop good sleep habits so that, most of the time, we get enough sleep,” added Malin, who was not involved in the study.
good sleep heals
To be healthy, the body must go through four stages of sleep several times in the same night. During the first and second phases, the body begins to slow down. In doing so, it prepares us for the third phase – deep slow-wave sleep, when the body literally recovers at the cellular level – correcting the damage caused by the wear and tear of the day and consolidating memories into long-term storage. .
Rapid eye movement sleep, called REM, is the final stage in which we dream. Studies have shown that a lack of REM sleep can lead to impaired memory and poor cognitive outcomes, as well as heart disease and other chronic conditions, and even early death.
On the other hand, years of research discovered that sleep, especially the deeper, more healing type, boosts immune function.
Since each sleep cycle lasts about 90 minutes, most adults need seven to eight hours of relatively uninterrupted sleep to get restful sleep, the researchers found. US Centers for Disease Control and Prevention.
Increased signs of inflammation
The study was small and involved only 14 healthy young people with no sleep problems. But the duration of the study was quite long, which gave it strength, McAlpine said.
“Many sleep studies are one day, two days, maybe a week or two,” he said. “But very few people look at the influence of sleep over a six-week period, so that’s what we did.”
All study participants wore wrist accelerometers, which allowed researchers to track sleep quality and duration every 24 hours. During the first six weeks, each study participant slept for the seven to eight hours recommended by the CDC for adults. For the next six weeks, they reduced their sleep by 90 minutes each night.
At the end of each six-week cycle, blood was drawn morning and evening and analyzed for immune cell reactivity. No negative changes were found in people who slept the appropriate number of hours. However, after study participants spent six weeks with restricted sleep, blood tests showed an increase in a certain type of immune cell when blood was drawn at night.
“This sleep restriction problem was very specific to one type of immune cell called a monocyte, whereas other immune cells did not respond,” McAlpine said. “It’s a sign of inflammation.”
Blood tests also detected epigenetic changes in monocyte immune cells after a long period of sleep deprivation. Epigenes are proteins and chemicals that look like freckles on genes, waiting to tell the gene “what to do, where to do it, and when to do it,” according to the National Institute for Human Genome Research. The epigenome literally turns genes on and off, often based on environmental cues and human behaviors, such as smoking, following an inflammatory diet, or experiencing chronic sleep deprivation.
“The results suggest that factors that can alter the expression in genes of inflammation-related proteins, called epigenomes, are altered by sleep restriction,” Malin said. “This change increases the risk that immune cells are more inflammatory in nature. The study did not perform functional or clinical tests to confirm disease risk, but it laid the groundwork for future studies to examine these mechanisms.
If epigenes can be turned on and off, will the change in immune function be sustained after study participants regain a full night’s sleep? The study was unable to investigate this outcome in humans. But the researchers did additional studies on mice that produced some interesting results.
Are the changes permanent?
Immune activity in sleep-deprived mice mirrored that of humans – immune cell production increased and epigenetic changes were observed in immune cell DNA. In these studies, the mice had 10 weeks of good sleep before being retested.
Despite getting enough sleep over a long period, the researchers found that the DNA changes persisted and the immune system continued to overproduce, making the mice more susceptible to inflammation and disease.
“Our results suggest that sleep recovery cannot completely reverse the effects of poor sleep in mice,” McAlpine said, adding that his lab continues to work with people to see if this result will translate to humans. man. (Note: rat studies often cannot be compared.)
“This study begins to identify the biological mechanisms that link sleep and long-term immune health. This is important because it is yet another key observation that sleep reduces inflammation, and conversely, sleep disturbances increase inflammation,” said study lead author Filip Swirski, director of the study. Icahn Cardiovascular Research Institute at Mount Sinai, in a statement.
“This work underscores the importance of adults getting seven to eight hours of regular sleep a day to help prevent inflammation and disease, especially in people with underlying medical conditions.”