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How sleep leads to healing after heart attack

The study sheds new light on how sleep helps the body to heal. Krakenimages.com / Shutterstock

Many studies in recent years have found links between sleep and heart health, and getting enough sleep has been shown to reduce the risk of heart attack. But less has been known about the role of sleep after a heart attack. It’s been unclear if and how heart damage might trigger changes to sleep patterns. Also unclear is whether such sleep changes might affect inflammation and recovery after heart damage. 

Recent studies suggest that the immune system plays a role in how the brain detects changes in heart physiology. The immune system is known to respond quickly after a heart attack. But how it might transmit information about the heart’s health status to the brain has not been well understood.

To learn more, a team of researchers led by Dr. Cameron S. McAlpine of the Icahn School of Medicine at Mount Sinai conducted a series of studies in both mice and humans. They examined the interactions between immune cells, the brain’s sleep circuits, and the impact of sleep on how the heart heals after injury. The study, which was funded in part by NIH, was published in Nature on October 30, 2024.

The researchers first assessed whether heart-related injuries could affect sleep. By studying mouse brainwaves, they found that immediately after a heart attack, mice spent much more time asleep and had a significant increase in deep sleep that lasted for at least a week. Deep sleep, or slow-wave sleep, is thought to be restorative, helping to strengthen tissues and immune function.

Additional analyses showed that after heart attack, immune cells called monocytes quickly accumulate in the mouse brain. This, in turn, triggers the monocytes to produce a protein called tumor necrosis factor (TNF). TNF then activates sleep-regulating nerve cells in the brain to induce deep sleep and healing. Studies of patients who died from heart attacks likewise showed that monocytes tend to gather in the human brain in the initial days after a heart attack.

To learn more about the effects of TNF-induced sleep, the researchers interrupted the sleep of some mice after a heart attack. Other mice were left to sleep undisturbed. The mice with poor sleep had worsened cardiac function, increased heart inflammation, and a higher death rate than mice with undisrupted sleep.

The researchers saw similar outcomes in studies of people. They examined data from about 80 patients with a cardiac condition that reduces blood flow to the heart. People who slept poorly in the following month had twice as many health problems during two years of follow-up than those who had healthy sleep patterns.

Taken together, the findings suggest that heart attacks trigger production of immune cells that rush to the brain, prompt restorative sleep, and aid recovery.

“Our study uncovers new ways in which the heart and brain communicate to regulate sleep and supports including sleep as part of the clinical care of patients after a heart attack,” McAlpine says. “Physicians should inform their patients to prioritize restful sleep during cardiac rehabilitation to help the heart heal and recover after a heart attack.”

—by Vicki Contie