Why shift workers are more vulnerable to heart problems: Risk of cardiac death could increase when heart cells get ‘out of sync’ with the brain and leave the body unable to cope, study finds 

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  • Experts explain why those working inconsistent hours have heart problems
  • Sporadic work hours disrupt the natural circadian rhythm of our heart cells
  • Heart cells control these circadian rhythms through changes in ion levels

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One study suggests that shift workers are more vulnerable to heart problems than people who work regular 9-5 jobs because of the disruption of the 24-hour natural clock in our heart cells.

In laboratory experiments with rats, researchers in London have identified the biological processes at play that make up the circadian rhythms of our heart cells.

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Circadian rhythms are 24-hour cycles that are part of the body’s internal clock, which run in the background to carry out essential functions and processes.

Experts report that when these circadian rhythms are disrupted by sporadic shift work and heart cells are ‘out of sync’ with the brain, the risk of fatal cardiovascular events can increase.

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Various systems of the body – such as our circulatory system – follow circadian rhythms that are synchronized with a master clock in the brain. ‘Heart clock’ controls daily changes in heart rate

Scientists have shown that heart cells regulate their circadian rhythms through daily changes in the levels of sodium and potassium ions.

circadian rhythms

Circadian rhythms are 24-hour cycles that are part of the body’s internal clock, which run in the background to carry out essential functions and processes.

One of the most important and well-known circadian rhythms is the sleep-wake cycle.

The various systems of the body follow circadian rhythms that are synchronized with a master clock in the brain.

This master clock is directly affected by environmental cues, especially light, which is why circadian rhythms are linked to the cycle of day and night.

When properly aligned, a circadian rhythm can promote consistent and restorative sleep.

But when this circadian rhythm is thrown off, it can cause significant sleep problems, including insomnia.

Research is also revealing that circadian rhythms play an integral role in diverse aspects of physical and mental health.

Source: Sleep Foundation

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Different levels of sodium and potassium ions inside and outside heart cells are important because they allow the electrical impulses that cause their contractions and drive the heartbeat.

It is already known that shift workers – those who work inconsistent hours during the week – are more vulnerable to heart problems. The new study suggests that it is because of these disruptions at the biological level of cells.

‘The way the heart functions around the clock becomes more complex than previously thought,’ said lead study author Dr John O’Neill, from the MRC Laboratory of Molecular Biology in London.

‘The ion gradients that contribute to heart rate vary in the daily cycle.

‘This likely helps the heart cope with increased demands during the day, when changes in activity and cardiac output are much greater than at night, when we normally sleep.’

Dr O’Neill believes this new understanding may lead to better treatments and preventive measures to deal with heart conditions.

“This opens up the exciting possibility of more effective treatments for cardiovascular conditions, for example by delivering drugs at the right times of day,” he said.

Circadian rhythm in mammals is a natural, intrinsic process that regulates the sleep-wake cycle independent of light and dark – and explains why we get jetlag.

Our circadian rhythm is regulated when we are sleepy and when we are more alert in a 24-hour cycle.

The various systems of the body follow circadian rhythms that are synchronized with a master clock in the brain.

This master clock is directly affected by environmental cues, especially light, which is why circadian rhythms are linked to the cycle of day and night.

It is already known that shift workers – those who work inconsistent hours during the week – are more vulnerable to heart problems (stock image of shift worker)

It is already known that shift workers – those who work inconsistent hours during the week – are more vulnerable to heart problems (stock image of shift worker)

However, lifestyles that oppose our natural internal clock – such as working the night shift – can ‘de-couple’ the internal circadian rhythms within heart cells from our behavior, the study shows.

The risk of cardiac death may increase when heart cell circadian rhythms are disrupted and ‘out of sync’ with the brain’s master clock, leaving the body unable to cope.

Dr O’Neill said, ‘Many life-threatening heart problems occur at specific times of the day, and most often occur in shift workers.

‘We think that when the circadian clocks in the heart are out of sync with those in the brain, such as during shift work, our cardiovascular system may be less able to cope with the daily stresses of working life.

‘This probably makes the heart more vulnerable to dysfunction.’

The worst type of shift work in this regard is working at night, when there is no sunlight, although any type of sporadic shift work that is inconsistent throughout the week can also disrupt heart cell circadian rhythms.

“The problem arises partly because when you go from day shift to night shift (or vice versa), you’re placing a demand on your body that goes against its natural circadian rhythm,” Dr. O’Neill told MailOnline.

‘While the circadian rhythm will adjust to a new routine (like jet lag), it takes several days and during this time our health is more vulnerable.’

Previously, cellular ion concentrations were thought to be fairly constant in cardiac tissue.

In experiments with rats, researchers found that heart cells actually change their internal sodium and potassium levels during the day and night to anticipate daily demands.

The video shows potassium (K), chlorine (Cl) and sodium (Na) ions moving in and out of heart cells, as well as changes in the concentration of certain proteins in the cell.

The heart has more sodium and potassium ions…

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