man sleeping

Changes in the circadian rhythm may mean that the resting heart rate rises slightly during the night, a new study shows. But is it so dramatic that we should slavishly go to bed at the same time every night – and what about when it’s the weekend?

Maybe you have changing working hours and alternate between day and evening shifts during the week.

Maybe you think it’s nice to sleep until 10 o’clock if you first have to meet at 12 o’clock, even though you usually get up at 7 o’clock.

But a new study shows that it is not a very good idea to vary the circadian rhythm.

It can lead to higher resting heart rate, both during the night and the day after, if we are to believe a new study, published in the journal Nature.

Not just the 8 hours that count

There is nothing new in the fact that the number of hours of sleep has a lot to say for our health – not least for how obvious and productive we feel the next day.

Maybe the number of hours we should sleep is a little overbearing in a stressful everyday life.

If we are to conform to the new study of researchers at the University of Notre Dame in the United States, we will at least have something to think about.

The researchers investigated the importance of a fixed circadian rhythm – that is, when we go to bed and when we get up, as well as the effect on the resting heart rate.

The study, which is based on 557 high school students, collected data from a total of 255,736 nights.

The resting heart rate increased briefly after previous bedtime

The researchers behind the study were based on two questions:

  • Can changes in the usual bedtime be linked to an increase in resting heart rate?
  • How long does it take for the resting heart rate to reach a normal level after bedtime deviations?

The resting heart rate is the number of heartbeats per minute in a person who is relaxing, and a normal resting heart rate is between 60 and 80 beats per minute, depending on the person.

It showed that:

  • When participants went to bed less than 30 minutes earlier than usual, the researchers found no significant difference in resting heart rate.
  • However, when participants went to bed more than 30 minutes earlier than usual, the researchers found an increase in resting heart rate.

It happened only during the night and mainly during the first hours of sleep, and the resting heart rate was stabilized before awakening.

Later bedtime had an effect on the resting heart rate the following day

It thus had no effect on the resting heart rate the following day, when the participants went to bed earlier .

The researchers, on the other hand, found that the later the participants went to bed, the more the resting heart rate increased.

They also found that that effect lasted until the following day and that the resting heart rate was not stabilized until 6 p.m.

  • When participants delayed bedtime by 30 minutes , it resulted in 0.26 extra heartbeats per minute.

Going to bed 2 hours later than usual results in theory in an extra heartbeat per minute.

Recommends getting up at a fixed time

What do we really know about the importance of the circadian rhythm from the past? In any case, it is nothing new that it plays a role, according to Dr Backhaus.

“We generally recommend not changing too much when it comes to going to bed and getting up. Usually we recommend is that you especially get up at a fixed time to maintain a fixed circadian rhythm, “he says and adds:

“Most advice is also that you should preferably go to bed at a fixed time, but to maintain a steady circadian rhythm, we especially recommend that you get up at a fixed time.”

But should we follow this advice slavishly – and what about the weekends?

“We are often asked, ‘Do you really think I should get up at the same time on the weekend as during the week I work?’ We usually allow you to relax a bit. We say a maximum of one – maybe two – hours later in the weekend than during the week, “says Dr Backhaus. He continues:

“But the difference should not be too great, because otherwise you can quickly have problems with the circadian rhythm and sleep worse than you would otherwise have done.”

Sleep and heart health go hand in hand

Dr Backhaus has not heard before that a varying circadian rhythm specifically has an effect on the resting heart rate.

“But we know that too little and too little sleep can generally affect heart health.”

What does it mean for the function in everyday life, if you now still have a very varied circadian rhythm?

“It can have many health consequences. First of all, a varied circadian rhythm – that is, getting up and going to bed at different times – will often lead to a mismatch between when you try to sleep and where the inner circadian rhythm is. ”

Many young people delay the circadian rhythm

There may be periods during life where we prefer not to spend time sleeping, but it is not a very good idea to relax at bedtime.

“Many young people delay the circadian rhythm, so they become extreme B-people, but in everyday life they have to live as A-people, because they have to get up early,” says Dr Backhaus and continues:

‘Then they end up shortening their sleep during the week. If your circadian rhythm tells you to sleep long and get up late, but you have to get up early, then you get too little sleep. ”

“It’s one of the problems: that the circadian rhythm does not match the demands placed on you.”

What about those who sleep well anyway?

Some simply have a really good sleeping heart; they fall asleep as soon as the head touches the pillow – no matter what time of day it is.

What about people who have shift work and a varied circadian rhythm – but who still sleep well? Is there also a health risk here?

“You will probably have a lot of health problems if you work very varied over a long period of time. We know that shift work and night work are associated with a lot of negative health effects, “says Dr Backhaus.

Some researchers believe that it is about changes in the circadian rhythm that affect a number of bodily processes – for example metabolism.

Metabolism encompasses all the chemical processes that keep us alive, such as the uptake, transformation, buildup, degradation and excretion of substances and the associated energy conversion.

Disorders can have a negative effect on health

Some researchers believe that disturbances in those systems can have a clear negative effect on health, says Dr Backhaus.

He says that it has been documented that shift and night workers have poorer health than others, or at least a greater risk of developing diseases, which other groups in society have less risk of.

»It has been shown, for example, that shift and night workers are at greater risk for a number of gastrointestinal disorders, such as ulcers in the stomach or duodenum. They have a greater risk of stroke and heart attack and of developing diabetes 2. Certain studies also show that shift and night workers have an increased risk of certain cancers such as breast cancer, prostate cancer and bowel cancer, “says Dr Backhaus.

The body’s internal clock is disturbed

He believes that the increased resting heart rate in deviations from the usual circadian rhythm indicates stress in the body.

“It simply came to our notice then. The physiology of the cardiovascular system is disturbed in some way. It is because you get too little sleep if you go to bed later than usual, «points out Dr Backhaus.

The cardiovascular system includes the heart and blood circulation – and thus also the regulation of the resting heart rate.

But that does not explain why the resting heart rate rises during the night if you go to bed earlier than usual – and in theory get more sleep.

clock genes
Clock genes

The clock genes play a role

So something happens to the resting heart rate during sleep when one deviates from the usual circadian rhythm, especially during the first hours.

Dr Backhaus thinks it may have something to do with the so-called clock genes.

»The clock genes are a rather complicated system in the body, and the circadian rhythm is regulated through various clock genes, as we say in the research. So it is clear that it affects the cardiovascular system in a negative way if disturbances occur in that system, “says Dr Backhaus.

It takes a few more hours before the resting heart rate increases by one beat per minute. But maybe it’s worth taking into consideration next Friday-Saturday if you’re the type who uses the weekend to postpone bedtime by several hours.