Is Resetting Clock Linked to Heart Attack Risk?

Every year, some 1.5 billion people around the world are subjected to the seasonal clock changes. But, are you aware that the act of adjusting clock has something to do with the heart attack risk?

Researchers from Karolinska Institute in Stockholm reported in the New England Journal of Medicine that because of sleep deprivation, there is a 5-percent increase in heart attacks in the week after clocks are reset for summertime.

In the spring, the risk of suffering a heart attack has been increased significantly in the week after clocks are set forward, while in the autumn, the risk of getting a heart attack has been reduced by 5 percent on average when clocks are set back an hour. In Europe, the clocks are set forward on the last Sunday of March and the clocks are set back an hour on the last Sunday in October.

Basing on the data from a comprehensive register of all heart attacks in Sweden between 1987 and 2006, the so-called “Karolinska Study” found that the changes in heart attack rates are closely related to the effect of sudden time change upon the sleeping patterns and biological rhythms. As such, the sleep quality and sleep duration is affected for those who are unable to adjust to the changes. In fact, growing body of evidence has shown that disruption of the biological rhythms and sleep problems could increase the risk of cardiovascular disease.

The shift in the spring disrupts the biological rhythm and sacrifices an hour of potential sleep, but the autumn shift will actually cause a disruption of the chronobiological rhythm and a possibility for some extra sleep. In other words, there are 2 different mechanisms working against each other for the autumn shift.

According to researchers, Monday has been considered as the most dangerous day of the week for getting heart attack. In fact, some previous studies have attributed such phenomenon to the sudden increase in activity and stress for the week ahead.

Meanwhile, the Karolinska study also explained why people suffer sleep deprivation when clock is reset: People usually get up later and go later to bed during the weekend, so if one goes to bed later on Sunday but still need to get up early on Monday, he or she will end up with a sleep deprivation.