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How circadian rhythms affect heart attack recovery

Disturbing circadian rhythms and sleep in the early days after a heart attack can hinder recovery. Here’s how new research could change that.
Young man sleeping in the bed It is quarter past seven in the morning

If you’ve ever spent a night in the hospital, you know that it can be almost impossible to sleep. Loud machines, bright lights and frequent interruptions throw off your body’s circadian rhythm – the internal clock that is crucial for regulating your body processes in health and disease.

A study led by Dr.Tami Martino, head of the Centre for Cardiovascular Investigations at the University of Guelph in Ontario, found that disrupting circadian rhythms and sleep in the days after a heart attack can hinder long-term recovery.

For most people, interrupting the circadian rhythm – at least in the short term – isn’t a big deal. Jet lag and daylight savings time throw off the body’s clock but it resets without any lasting effects. But when you’re recovering from a physical trauma like a heart attack, you don’t bounce back the same way.

Until recently, the body’s internal clock was seen as an alarm clock and little else. In reality, it’s command central; a master scheduler that coordinates every biological task the body needs to carry out.

Nighttime is when general maintenance and repair work happens. In the event of an injury, the body deploys its innate immune response; a biological clean-up crew that clears away dead cells and debris. A disruption to sleep in those first few days prevents the immune system from properly coordinating its job.

As Dr. Martino’s team discovered in a previous experimental study, that initial disruption leads to what she describes as a domino effect. Debris isn’t properly cleared away in the first stage of the immune response, so damaged areas of the heart don’t heal as well as they could. The experimental research study showed that scars tend to be larger, the heart dilates, and can progress to heart failure – the result of damage that leaves the heart too weak to pump blood properly.

How sleep affects recovery

That sleep is essential for recovery isn’t a new revelation. Historically, medical professionals like Dr. Eugene Braunwald, father of modern cardiology, realized disrupting patients’ sleep was a bad idea. But they didn’t have the science to back up this idea.

By the 1960s, the first coronary care units were developed to consolidate the doctors and resources that they needed to help patients who had a heart attack, Dr. Martino explains. But they unknowingly created an environment that resulted in disturbed sleep and circadian rhythms.

Overhauling hospital rooms isn’t entirely practical. And it might not be necessary. In the next phase of her study, supported by Heart and Stroke Foundation donors, Dr. Martino is investigating how to target later immune responses to improve recovery.

Until now, no treatment was available to halt the damage that can result when sleep and circadian rhythms are disrupted after a heart attack. However, the arrival of new circadian rhythm drugs could change this. Dr. Martino will investigate if these drugs can be used to reduce the circadian disruption and benefit healthy healing processes for the heart.

The drugs would only be needed in the earliest days of recovery and if successful, could ultimately improve healing and reduce the progression of heart failure.