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Prof. Domien Beersma: ‘Change from summer time to winter time is unhealthy’

24 March 2009
Next week, half the Dutch population will feel tired and under the weather. Moreover, around five percent more heart attacks will occur than in an average week. The cause: the transition from winter time to summer time. The biological clock has an immense effect on our health, and not just during changes from winter time to summer time. Everyone knows this from personal experience and there is increasing scientific evidence in support. However, this knowledge is rarely put to good use. That is a shame, says chronobiologist Prof. Domien Beersma.
Next week will be difficult for many people, since it will be the week after the transition to summer time. Research has shown that particularly nocturnal people find it hard to adapt to this change. They do not feel tired in the evening and their biological clock tells them that they can stay up for another hour or so. The following morning, however, their boss will not look at their employee’s biological clock but at his wristwatch, which he has just advanced one hour. Thus they have to get up at a time when their body is not quite ready.

More stress, more heart attacks

It has been known for some time that the increased stress accompanying the change from winter time to summer time leads to more road accidents. Recent studies have shown that the number of heart attacks rises by five percent in the first week after the transition. Beersma: ‘Swedish researchers have recorded exactly when heart attacks occur. They found that there is a peak on Monday throughout the year. The number of heart attacks declines during the week and is lowest during the weekend. After the transition to summer time, the Monday peak is much higher. But the number of heart attacks remains higher than normal during that whole first week’.

Health benefits

However, this ‘winter to summer’ change is not what occupies Beersma most. More importantly, he says, is that we are at the mercy of our biological clock throughout the year. ‘We should take our chronotype much more seriously; in other words, are we diurnals or nocturnals, larks or owls? What good is it to an employer if his employees have to drink one cup of coffee after another just to stay awake? What can teachers achieve when most of their pupils are half asleep over their books? I say, let people work when they are at their best. That will not only result in health gains but also have economic benefits. If all of us no longer have to be at work by nine o’clock, traffic queues will be shorter, for example.

Accurate to the minute

It has been known since 1972 that two small cell clusters in the brain – more precisely, the suprachiasmatic nucleus situated immediately above the site where the two optic nerves cross – influence our circadian rhythm. It is slowly becoming clear that these cells not only tell us when it is time to go to sleep or to wake up. Beersma: ‘It seems that our biological clock can provide very detailed information and is able to activate all sorts of organs with an accuracy to within one minute’. What we now know about increases in traffic accidents and heart attacks is therefore only the tip of the iceberg, Beersma believes. ‘From organs to the immune system, everything is influenced by those two cell clusters. This will become much more evident in the coming years’.

Sleep behaviour of the Dutch

Much research is required to unravel the mechanisms underlying the biological clock. Groningen researchers are conducting experiments on the effects of sleep deprivation and light of various colours, for example, and are also studying the circadian rhythms of yeasts and fungi. But interesting insights can also be obtained outside the laboratory. Beersma: ‘By collecting as much data as we can about the sleep behaviour of the Dutch population, we hope to get a better understanding of the functioning of the biological clock. Anyone interested in their biological clock and giving a helping hand to science can fill out a questionnaire at our website,’.

Curriculum Vitae

Domien Beersma (1951) is a Professor at the Faculty of Mathematics and Natural Sciences of the University of Groningen and has an international reputation in the field of human chronobiology (the ‘biological clock’). Until 2001 he worked at the Biological Psychiatry department of University Hospital Groningen (now UMCG) where he studied the relationship between the biological clock and winter depressions. His current field is the fundamental and theoretical aspects of human and animal circadian rhythms.

Last modified:04 January 2018 3.36 p.m.
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