Why is the risk of heart attack higher early in the day
➤ In the journal Circulation, a team led by IPEK scientists Maliheh Nazari-Jahantigh and Andreas Schober provides an answer.
![CHUTTERSNAP | Unsplash](https://cdn.lmu-klinikum.de/5e56e35ef7be6818/c52ab221c7e1/v/8b282cbe4935/Clock-chuttersnap-unsplash.jpg)
The risk that an atherosclerotic plaque will rupture varies with the time of day. That’s why heart attacks and strokes are more likely to occur in the morning than at other times.
A normal day/night schedule of activity reduces the risk of heart attack, but circadian processes that take place within plaques can enhance the risk of rupture. The action of microRNA-21 causes more cells in plaques to die at the beginning of the active phase in the morning – at a time when they cannot be disposed of efficiently. The ensuing accumulation of dead cells amplifies the risk of plaque rupture.
![Circulation 2021 Schober](https://cdn.lmu-klinikum.de/6c200694e44640c6/0b82aaf867c4/v/12d174297b28/Circulation-2021-Schober.png)