Summer jet lag? Here's how to get back into the rhythm

It runs day and night, but you rarely think about it: your biological clock. However, it sometimes makes its presence felt, for instance when you fly to a distant country. So how does the clock actually work? Are there really night owls and morning people? And how do you get back into the swing of work quickly after long summer holidays? We asked health psychologist Esther Habers.

How does the biological clock actually work?
“The internal biological clock regulates our circadian rhythm, a cycle lasting 24 hours. This 24-hour rhythm is mainly controlled by the suprachiasmatic nucleus, SCN for short, a group of cells deep in the brain. The nucleus controls the sleep-wake rhythm by stimulating other regions of the brain, such as the pineal gland, which produces melatonin when it gets dark. The SCN controls many different processes in the body.” (see box)

Do all animals have biological clocks?
“It goes even further than that. It seems that all organisms have them. The biological clock originated very early in evolution and enables us to anticipate what’s to come. The clock regulates not only the circadian rhythm but also the annual rhythm, for example in birds that fly south when it gets cold.”

Does the clock need light to stimulate it?
“The SCN also works without light. In experiments where people saw no daylight for long periods of time and had to organise the day themselves in terms of lighting, their rhythm shifted to a day lasting 25 hours. When they were exposed to daylight again, the 24-hour rhythm quickly returned. So, daylight resets the SCN.”

As a night owl, a 25-hour day sounds great! Do morning and evening people really exist?
“Absolutely. There’s been a lot of research into this. Evening people would like to have a slightly longer day than morning people. It seems to be partly genetically determined. From an evolutionary point of view, communities benefited if they had people to keep watch in the evening and others to do so early in the morning.”

Does a person’s age and sex influence the rhythm?
“During puberty, men (but many women too), exhibit typical ‘night owl’ characteristics. This might possibly be due to an increase in sex hormones. At the same time, you can see that boys’ daily rhythm ‘stretches’ a bit further than that of girls by an average of around 45 minutes. This process peaks at around the age of 20. In the years that follow, the rhythm becomes earlier again and the difference tapers off. By about 50, it has disappeared.”

How does working at night affect your circadian rhythm?
“It’s really unhealthy! It completely disrupts the biological clock. In the short term, it causes concentration problems and affects the memory. It also interferes with metabolism, which in the long term can result in diabetes and obesity. The 24-hour economy is really not suited to people at all.”

What’s the best thing to do when you are jet-lagged due to a large time difference?
“Adapt to the local sleeping and eating times as quickly as you can. For each hour of jet lag, you should reckon around one day for the body to get used to the new time zone.”

Do changes to and from daylight saving time also have an effect?
“That transition is actually like a mini jet lag. Most people get used to it after a few days, but some have a stronger reaction.”

Why is it so hard to get back into the swing of work after long summer holidays?
“When on holiday, many people sleep in longer and go to bed later. This means they have a later exposure to light, causing their biological clocks to shift slightly. For the first few days back at work, you’re still in sleep mode in the morning. But morning people don’t have as much trouble with it because they still get up early even when on holiday. Some tips: a few days before your holidays end, start going to bed and getting up earlier, don’t use your smartphone late at night, dim the lights earlier and make sure you get plenty of light in the mornings. This will help your biological clock quickly get back in time with your work rhythm.”

That nucleus with the long name is quite an important little organ…
“The body is like a symphony orchestra: if all individual cells and organs are properly in tune with each other and with the environment, you get a harmonious result. When it comes to your biological rhythm, the suprachiasmatic nucleus is the conductor!”
Ronald Touw

Boléro

Rise to the Rhythm

Saturday, September 21

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