Researchers have long observed that serious heart rhythm problems are more likely to happen in the morning.
Despite numerous studies, the exact reason behind this timing remained a mystery, until now.
Scientists at Imperial College London have made a breakthrough, linking these dangerous heart rhythms to a morning surge in cortisol, the stress hormone that naturally peaks when we wake up.
In detailed experiments with mice, the researchers discovered how cortisol plays a critical role in this process. They found that cortisol attaches itself to a specific receptor inside heart cells.
This receptor then moves into the cell’s nucleus, where it affects genes that control ion channels in the cell’s outer layer. These channels are essential for managing heartbeats.
With the changes induced by cortisol, the heart becomes more prone to arrhythmias because the regular electrical impulses, which ensure steady heartbeats, can easily become erratic.
The study highlighted cortisol’s circadian rhythm, which is influenced by sleep patterns, showing a significant increase right before waking. This insight not only explains the timing of these heart rhythm issues but also opens the door to potential new treatments.
By testing on mice, Dr. Alicia D’Souza and her team demonstrated that injecting a drug that blocks the cortisol receptor can prevent the morning shift in ion channels, thereby reducing the risk of arrhythmias at this critical time of day.
Dr. D’Souza, from the National Heart and Lung Institute at Imperial, emphasized the importance of our internal biological clock in this process.
“Our hearts behave differently at various times of the day, being most at risk in the early hours due to ancient circadian rhythms shared across species. While our study was conducted on mice, we’re confident that the findings are relevant to humans and other mammals,” she said.
This connection between cortisol and heart rhythm disturbances has significant implications for preventing sudden cardiac events, which can occur without warning and lead to sudden death if not promptly treated.
Professor James Leiper from the British Heart Foundation highlighted the importance of understanding the causes of these arrhythmias to develop effective prevention strategies.
The study, published in Circulation Research, is part of ongoing research by Dr. D’Souza and Professor Mark Boyett into the day-night rhythm of the heart’s electrical activity and its susceptibility to arrhythmias.
Their findings not only solve a part of the puzzle of why our hearts are more vulnerable to disturbances in the morning but also suggest new pathways for treatment, marking a promising step forward in cardiac care.
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The research findings can be found in Circulation Research.
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