Daylight Saving Time

Did you remember to change all your clocks for the bi-annual Daylight-Saving Time?
Clocks worldwide changed tonight: time magically jumped from 02:00 to 3:00, and we lost 1 hour of sleep. This is inconvenient and affects our body clocks. However, Daylight-Saving Time has been related to various heart risks. Indeed, in 2018, the European Parliament voted on the possibility to stop the Daylight-Saving Time (DST), based on health concerns.

To understand why our heart can be affected by the DST, let’s take a dive in our body. We all have a circadian rhythm which originates from Latin “circa” meaning “around” and “diem” meaning day. We have several internal clocks, one of which is a group of 20’000 neurons located in the hypothalamus and called the “master clock”. This clock has an influence on various functions such as sleep/rest patterns, locomotion, feeding and drinking behaviours and body temperatures. It releases different components such as hormones for bodily functions during the day.

On top of the nervous system, our cardiovascular system also has its own biological clock located in the cardiomyocyte (cells of the heart muscles). These cells directly influence the heart muscles and play a role in the sleep/rest cycle as well as feeding and fasting cycles. One of the function of this “cardiac clock” is to help the heart adapt to a prolonged fasting time for example. A desynchronization of the environment, such as a time change, leads to disturbance in the circadian clock of heart cells and can thus increase risks of cardiovascular accidents. One of the most studied heart risks in time frames are heart attacks (acute myocardial infarction). It has been shown that these incidents have 40% more chances to occur in the morning. Aortic aneurysm as well as cerebrovascular events have also shown to occur more frequently during the morning.

The reason is that in the morning, we have an increase of

  • Sympathetic activity: leading to a faster heart rate for example
  • Vasoconstrictive hormones
  • Platelet aggregability

How is this relevant to DST?
During DST, we are deprived from 1 hour of sleep. This leads to even more stress in the body in the morning. It has been shown that during the week following the spring DST, heart attacks increase from 4-29% depending on the studies. It has also been shown that risks are higher when the DST occurs on Mondays as people do not have the possibility to sleep in. Moreover, lack of sleep leads to higher risks of obesity, diabetes, coronary heart diseases and hypertension. Eventhough some studies suggest that women have higher risks to be affected by DST, it has not been proven that gender plays a role in the risk of cardiovascular events following DST.

“ En avril, ne te découvre pas d’un fil” – “April showers bring May flowers” – “Alles neu macht der Mai”

This old saying might not be that obsolete. Indeed, one other reason of higher health risks following the DST is that we spend more time outdoors and could lead to more exposure to cold temperatures.

To prevent any health risks after DST:

  • Try and move your bedtime 1 hour earlier a few days before time shift
  • Clothe yourself appropriately

It’s the quarantine anyways so it is easier to sleep in and not go out in a whim!


From asep, with love.


Horia – President



Leave a Reply