A late-night taxi carries a soulless body home from overtime until 3am The food stalls and nightclubs are full of people, the convenience stores that do not close are always visited by night owls, and the emergency department of the hospital is also full of all kinds of patients… In our enjoyment of “24-hour society” “Behind the convenience it brings, countless night shift workers have paid for their sleep and health to keep the city running at night. People who work night shifts often have trouble sleeping during the day, and rely on cigarettes and coffee to wake up at night.Should not sleep, they will collapse sooner or later, and those who work night shifts for a long time People not only have heavier dark circles than others, but even the area of myocardial infarction is larger than others! A study by Bu Jun’s team from Renji Hospital Affiliated to Shanghai Jiaotong University showed that long-term night shift work is associated with increased myocardial infarction size in patients with myocardial infarction, not only that, Night workers had a 92% higher risk of major adverse cardiovascular events than day workers within 5 years of MI! And the adverse effects of night shift work on the heart are mediated by the NR1D1/CLCF1 pathway. The study was published in the Journal of the American College of Cardiology. 
A total of 412 patients with ST-segment elevation myocardial infarction were included in the study, with an average age of 58 years and 93% males. People (24.8%) need to work night shifts for a long time. Compared with day workers, they were younger (50 vs 59),higher BMI (25.43kg/m2 vs 24.71kg/m2), and more likely to smoke (75.5% vs. 62.9%) and a higher incidence of hyperlipidemia (57.8% vs 47.7%). All patients underwent percutaneous coronary intervention (PPCI) within 12 hours after the onset of myocardial infarction, and cardiac magnetic resonance was performed to assess myocardial infarction size about 5 days after the operation. (Therefore, the size of myocardial infarction described below refers to the size of myocardial infarction after ischemia-reperfusion.)After adjusting for possible confounding factors such as age, gender, BMI, smoking, After hypertension, hyperlipidemia, diabetes, and cardiac function Killip classification, the researchers found that:also experienced myocardial infarction, and compared with day workers,more often The area of myocardial infarction was significantly increased in night shift workers (β=5.94%; 95% CI: 2.94–8.94; P < 0.0001);risk of microvascular occlusion (MVO) Doubled (OR: 2.28; 95% CI: 1.26–4.12; P = 0.006); lower left ventricular ejection fraction(β =-4.1%; 95% CI: -6.5 to -1.5; P=0.002). 
After myocardial infarction, the researchers followed up the patients for an average of 5 years, with 19.2 % of patients experienced major adverse cardiovascular events, including 6 deaths, 14 myocardial reinfarction, 48 heart failure, and 7 stroke. Night work was still associated with the risk of major adverse cardiovascular events, and after adjustment for possible confounding factors, compared to daytime workers who worked night shifts more often. People had a 92% increased risk of major adverse cardiovascular events(HR: 1.92; 95% CI: 1.12-3.29; P=0.017);increased risk of heart failure106 % (HR: 2.06; 95% CI: 1.073.96; P=0.03). 
However, the above observational studies can only show that there is an association between night work and myocardial infarction, but cannot prove that night work directly causes myocardial infarction in patients. increase, the prognosis is worse. As a result, the researchers began to “sharpen the knife to the mouse”, disrupting the mouse’s normal circadian rhythm by regulating the light-dark cycle in the mouse’s living environment (lights out during the day, lights at night). to simulate “working the night shift”. After 8 weeks of night shifts, the mice underwent ligation and re-opening of the left anterior descending artery of the heart to simulate myocardial infarction after ischemia-reperfusion. Consistent with those observed in humans, mice myocardial infarctions that were forced to “work the night shift” after surgery The area is significantly larger than that of mice with normal routine, lower myocardial vitality, and worse cardiac function. After myocardial infarctionThe mortality rate is also higher, which strongly proves that the circadian rhythm disorder caused by “working night shift” can really aggravate myocardial infarction injury and affect the prognosis of the mice. 
Not only that, considering that the hearts of mice are much smaller than those of humans, the researchers also focused on large animals (sheep) Similar experiments were carried out, and similar results were obtained: The size of myocardial infarction formed after ischemia-reperfusion surgery in sheep on night shift for 12 weeks was larger than that in sheep with normal work and rest. More heart cells, lower left ventricular ejection fraction, hammer on hammer. 
(What are you doing?)Next, let’s explore why “working the night shift” is bad for the heart so affected? The researchers’ first thought was that “working the night shift” disrupted normal circadian rhythms. By analyzing the changes in circadian clock gene expression under the condition of “working night shift”, the researchers found that “working night shift” decreased the expression of NR1D1 gene, and increased the expression of BMAL1 and PER1 genes in the heart circadian clock of mice and sheep, but the expression of BMAL1 and PER1 increased in mice and sheep. In the heart after “ischemia-reperfusion surgery”, “working night shift” only reduces the expression of NR1D1 in the heart with myocardial infarction. In order to study the role of the NR1D1 gene in the process of myocardial infarction, the researchers specifically knocked out the NR1D1 gene (Nr1d1 cKO) in mouse cardiomyocytes, and then gave these mice “deficient mice”. The results showed that the myocardial infarction area of Nr1d1 cKO mice was significantly larger than that of normal mice, and the myocardial activity and cardiac function were also worse. However, injecting NR1D1 agonist into mice after “ischemia-reperfusion” surgery, or expressing NR1D1 in mouse cardiomyocytes can significantly alleviate the exacerbation of myocardial infarction caused by “night shift” , improve myocardial damage and cardiac function. After further analysis, the researchers found that the decrease in the expression of NR1D1 gene in cardiomyocytes would increase the expression of the downstream CLCF1 gene (a member of the IL-6 family), which eventually led to the increase in the expression of inflammatory factors in cardiomyocytes, attracting peripheral Neutrophil infiltration aggravates myocarditis and edema. To sum up: “Night shift” affects the biological clock, resulting in a decrease in the expression of the cardiac biological clock gene NR1D1, aggravating the inflammatory response during myocardial infarction, and increasing the myocardial infarction area. Affect cardiac function and worse prognosis. ”
Finally, for how to reduce the impact of “night work” on the heart, the researchers said, reduce the frequency or duration of “night work” Time may be beneficial to the cardiovascular health of night shift workers, and more research is needed in the future.After all, some jobs always need someone to do, take doctors as an example,Super 6 Cheng doctors work night shifts twice a week, among which residents are the most frequent.(Data from the “Physician Health Status Survey” of Yimi Research)< span>, the night shift fee of 40 yuan can be said to be hard-earned money.As for those hospitals that do not pay the night shift fee and ask for the refund of the night shift fee on the grounds of “distributing allowances in violation of regulations”, I just want to :
(image source network)
References:
[1].Zhao Y, Lu X, Wan F, et al. Disruption of Circadian Rhythms by Shift Work Exacerbates Reperfusion Injury in Myocardial Infarction. J Am Coll Cardiol. 2022;79(21):2097-2115. May SevenEdit | Alaska Treasure
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