Increased double product on Monday morning during work.

It has been reported that cardiovascular events often occur on Monday morning, especially in the young working population. Because hypertension is a major cardiovascular risk, we examined whether blood pressure was elevated on Monday, especially in the morning during work. However, there were no weekly rhythms in blood pressure itself. Instead, we found significant interactions between the double product (systolic blood pressure × heart rate) and weekly (high on Monday) and circadian (high in the morning) rhythms. Further studies are required to determine whether Monday morning preference in cardiovascular events is caused by increased double product.