Tired from summer time

The clocks will be put forward an hour in the night of Saturday 26th to Sunday 27th March, heralding the start of summer time. For some people it takes a week or more to adjust. Why is this? And why does it affect some people and not others?

National Sleep Day

Summer time causes extra problems for night owls

It's not by coincidence that the Dutch Association for Sleep and Wakefulness Research (NSWO) is holding its annual National Sleep Day on 26 March, the last day of winter time. 'We do this every year,' comments Dr Kristiaan van der Heijden, sleep researcher at the Institute for Education and Child Studies and PR man for the NSWO. ‘It's a good time to stop and think about healthy sleep and the negative effects of feeling tired.' This is certainly something a lot of people suffer from once the clocks are changed.

Early birds and night owls

‘Our bodily processes exhibit a 24-hour rhythm,' explains neurophysiologist Professor Joke Meijer. ‘These processes are driven by a group of cells at the base of the brain, the so-called biological clock. These cells produce rhythms lasting a little longer than 24 hours, something like 24.2 hours for early birds, and almost 25 hours for night owls. This explains why night owls have so much difficulty waking up in the morning and going to bed on time. When we change the clocks, we have a day of just 23 hours. That's particularly difficult for night owls, but no problem at all for early birds.'

Half asleep

Dr Kristiaan van der Heijden: 'Changing the clock doesn't result in more traffic accidents.'

When the clocks are changed, the normal and biological clock are no longer synchronous: the alarm goes off while your body thinks you should still be asleep for another hour. As a result your brain is not properly alert, so you feel sleepy and function less well mentally. This can give rise to dangerous situations, if drivers get behind the wheel of their car while they are still half asleep, for example. Van der Heijden: ‘In 2010 we investigagted whether there were more car accidents after the change from winter to summer time and vice versa, but this didn't appear to be the case. Maybe people are aware of the danger and take extra care, drinking an extra cup of coffee before leaving home.'

Adapt

Our biogical clock can return to its natural rhythm relatively quickly. Maijer: 'You adapt within a couple of days, a week at most. The important thing is to start to live in line with the new clock times, and make sure you get as much daylight as possible in the morning. A wake-up light that imitates sunrise, doesn't help. The light is too weak.'

Abolish summer time

Prof. Joke Meijer: 'The biological clock consists of a group of cells at the base of the brain.'

Would it not be a better idea to abolish summer time? Meijer believes on the basis of her professional discipline that there are grounds for this. 'But the arguments from different disciplines have to be compared. Does summer time give any benefit in terms of energy use, for example? These are all matters that have to be taken into account in such a decision. I also think this is an issue that has to be looked at Europe-wide.'

Children

Van der Heijden, too, thinks that the question of whether or not to abolish summer time is a matter for the energy experts, but he believes that it might benefit children. 'When it gets dark earlier, they fall asleep more easily. Our research has shown that in general children sleep too little and that they therefore perform less well in mental tasks in the morning than in the afternoon. Abolishing summer time might have a beneficial effect on their school performance.'