Last weekend we shifted again from summer time to winter time. I actually prefer this specific transition, because we gain an extra hour. It is also the time of the year were the ongoing discussion about a permanent time (summer or winter) lights up and keeps the media busy. It might even be the last time! When I listen to the people around me (the non-sleep sleep scientists), I notice that most of them don’t have a clue what the core of this discussion is actually about and what the concrete consequences would be for their daily life if we would choose a permanent winter- or summertime.
In order to explain this, we need to dive into our brain and clarify how daylight affects our sleep-wake rhythm. Our sleep system consists of 2 important processes (2-process model of Borbély, 1982) who interact with each other: Proces S, a homeostatic process which reflects our sleep pressure or need for sleep, and process C, our circadian clock, which programs sleep and other physiological processes in our body. Changes in body temperature, blood pressure, hormone productions, digestion, attention and concentration, memory processes, are all seamlessly aligned and organized. As such, every morning, our brain has a 24-hour plan ready with all the necessary steps in the right order. Just a matter of being well organized and prepared! In order for this clock to work properly, it needs to be stimulated by light every morning (and not in the evening!) to start up and adjust this 24-hour plan. That is our ‘green’ light! Our ‘Go’!
Summer time was originally set in so we could enjoy daylight for a bit longer during the summer evenings and as such, also save on electricity costs. Most people associate this with cosy evenings on the terras, enjoying a beautiful sunset. No wonder people tend to choose a permanent summer time! As if this mental picture would be prolonged for the rest of the year. However, nothing could be further from the truth! The real problem in this situation are the mornings. The reason why we shift back to winter time at the end of October, is because the sun is gradually coming up later and later. Delaying that light stimulation we so eagerly need! This has a serious impact on our brain and body. We are deprived of morning daylight which results in increased fatigue in the morning, even when our alarm clock sets off at the same time as ever (At least I hope it does, otherwise we will need to have another serious talk). When it used to take half an hour to shake of the morning grogginess or fatigue, it now takes an hour or even more. It can have an effect on your feeling of being hungry in the morning, resulting in skipping breakfast or eating not enough. It affects your bloodpressure, attention and concentration span. It can even have an impact on melatonin production in the evening. All these changes are correlated with increased car accidents in the morning. Our kids are deprived of that necessary ‘starting shot for the brain’ and at risk for sleep deprivation. This results in a delayed and disrupted activation of the cognitive system (attention, concentration, memory and learning ability), undermining their general academic performances. It can result in insomnia complaints and sleep shortage in adults. I can continue for a while discussing the detrimental effects of this on both humans and society… Despite the clear scientific prove in favor of permanent wintertime over summertime, the European Parliament, and the majority of the people tend to choose for permanent summertime. So we could enjoy our beer or glass of wine a bit longer outside during those summer months? Really??
Or do we dare to choose in favor of our health on the long term? Do we choose to give our kids the opportunity to perform better and develop in a physiologically more appropriate way? Do we support humans during those dark winter months by making sure our basic need for morning light is met? Do we choose to improve our sleep by allowing less light during the evening, and adapting to our natural need for darkness that time of the day?
This is a decision not to be taken lightly. In the current society, too often humans need to adapt their physiology in favor of technological, economical or political causes. The results of these decisions can no longer be ignored. So please, let’s have the courage to put our health at first place. A society that adapts to our human physiology, in stead of the other way around.