Why the risk of heart attack is higher early in the day

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.

Andreas Schober, Richard M. Blay , Saffiyeh Saboor Maleki, Farima Zahedi, Anja E. Winklmaier, Mati Y. Kakar, Isabelle M. Baatsch, Mengyu Zhu, Claudia Geißler, Anja E. Fusco, Anna Eberlein, Nan Li, Remco T. A. Megens, Ramin Banafsche , Jörg Kumbrink, Christian Weber, Maliheh Nazari-Jahantigh: MicroRNA-21 Controls Circadian Regulation of Apoptosis in Atherosclerotic Lesions. Circulation, 2021