Heart Attacks Can Be Worse at Certain Times of Day
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Introduction: Why Timing Matters in Heart Health
We often hear that heart attacks can strike at any time—but did you know that the severity of a heart attack can actually depend on the time of day it happens? A new discovery has revealed that our body’s internal clock plays a key role in how the heart responds to injury. This insight could lead to better treatment strategies and possibly save lives.
Understanding the Body’s Clock
Our bodies follow a natural 24-hour cycle known as the circadian rhythm. This internal clock controls many functions, including sleep, metabolism, and even how organs respond to stress. In the heart, this rhythm affects blood pressure, heart rate, and hormone levels throughout the day and night.
Special proteins help keep this rhythm running. Two of the most important are BMAL1 and HIF2α. These proteins switch genes on and off at specific times, helping the body react properly to changes, such as low oxygen during a heart attack.
What Happens During a Heart Attack
A heart attack occurs when blood flow to the heart is blocked, leading to ischemia (low oxygen) and damage to heart muscle tissue. When blood flow returns (called reperfusion), the damage can actually get worse before the heart begins to heal.
In new research with mice, scientists found that the time of day when the heart attack occurred made a big difference. Heart tissue was less damaged in the afternoon, when the levels of BMAL1 and HIF2α were naturally higher. In contrast, heart damage was more severe at night, when levels of these helpful proteins were lower.
How These Proteins Help Protect the Heart
BMAL1 and HIF2α work together to turn on a gene called Areg, which makes a protein called AREG. This protein helps heart tissue repair itself. When BMAL1 levels are high, more AREG is produced, which helps protect the heart from serious damage.
When BMAL1 levels are low, AREG isn't made in time, and the heart suffers more damage. This means the body’s clock is not just about sleep—it also plays a role in healing after a heart attack.
Could Timing Improve Heart Treatments?
The idea that treatment could be more effective at certain times of day is called chronotherapy. In the mouse study, scientists gave treatments like BMAL1-boosting and HIF2α-stabilizing drugs at different times of day. The results showed better recovery when the timing of the treatment matched the natural rhythm of these proteins.
For example:
- A drug called nobiletin, which boosts BMAL1, worked best when given at night (when BMAL1 is low).
- Another drug, vadadustat, which supports HIF2α, was most effective when BMAL1 was naturally high.
- Giving AREG protein during blood flow restoration also reduced heart damage—especially when BMAL1 levels were at their lowest.
Why This Matters for People
These findings from mice were supported by data from human heart tissue. People who had heart procedures showed similar time-of-day patterns in their heart gene activity, suggesting that these results may apply to humans too.
This research could eventually help doctors decide the best times to give heart medications or perform procedures, to maximize healing and reduce damage.
Conclusion: Timing Could Be a Heart Saver
This new understanding of how the body’s internal clock affects heart attacks gives us a powerful new tool. Not only does it explain why heart attacks may be worse at certain times of the day, but it also opens the door to smarter, more personalized care.
While more studies are needed in humans, the future of heart care might include something as simple—and as powerful—as looking at the clock.