2024-10-27 06:07:00
On the night of Saturday October 26 to Sunday October 27, France switched to winter time. An important change for our biological clock, which can also have harmful effects on health, warns Inserm.
Fatigue, difficult sleep, low morale… On the night of Saturday October 26 to Sunday October 27, the French switched to winter time. While some particularly enjoyed sleeping an extra hour – at 3 a.m. it was actually 2 a.m. – others are already feeling the effects of the time change.
Established in 1976, this device, which always occurs on the last Sunday in October, was originally intended to save energy by matching the hours of daily activities to the hours of sunshine and thus reduce the time artificial lighting in the evening.
If for most people, the time change has no impact on daily life, several scientific studies have demonstrated that this change impacts our biological clock and thus has significant effects on our health.
Biological clock disorders
Among the harmful consequences of the time change, we find in particular sleep disorders, fatigue and mood changes. The National Institute of Sleep and Vigilance (INSV) also notes an increase in the number of car accidents, myocardial infarctions and depressive states. So how can we explain the impact of the time change on our health?
Whether it is the transition to summer or winter time, the time change systematically induces a one-hour shift in relation to our biological clock, called the circadian system.
Concretely, almost all functions of the body are subject to the circadian rhythm, that is to say a 24-hour cycle. Thus, disrupting this rhythm can have consequences on sleep as well as on metabolism, the functioning of the cardiovascular system or the immune system.
Besides, we are not all equal when it comes to the time change. “Small children and the elderly are more likely to feel negative effects, but this is also the case for adolescents, night workers, and all those suffering from a sleep disorder,” points out the Institute. National Health and Medical Research (Inserm).
Standard Time vs. Daylight Saving Time
According to Inserm, the time change does not have the same impact on the body whether it is the change to winter time or the change to summer time. The latter would be more complicated to bear given the loss of an hour of sleep and the fact that the biological clock will have to be advanced by an hour.
The effects of the switch to summer time would be all the more accentuated by the general lack of sleep of the French population which is estimated at 60 minutes per day according to the 2022 barometer of the National Institute of Sleep and Vigilance .
Another difficulty, reminds Inserm, during the day, we generally accumulate a delay of 10 minutes on our 24-hour cycle. However, in fact, the transition to summer time requires our body to advance its rhythm by one hour, which further accentuates the efforts made by our body to try to catch up and de facto causes a state general fatigue.
For “permanent winter time”
In 2019, the European Commission proposed a directive to put an end to seasonal time changes. The text provided that each member state of the European Union decides whether it wants to stay permanently on summer time or winter time.
56% of European citizens said they were in favor of “permanent summer time”, while 32% said they preferred winter time. In view of these results, however, the scientific community calls for caution.
“If we were to maintain summer time all year round, waking up in winter and going to bed in summer would indeed be more difficult,” warns Inserm.
“On the shortest day of the year, December 21, the sun would rise in Paris at 9:41 a.m., instead of 8:41 a.m. (winter time, editor’s note),” continues the Institute. However, “a very late sunrise in this winter season would have a harmful impact on the health of the French”.
Exposure to light and sport recommended
Works of Lyon Neuroscience Research Center have proven the importance of exposure to light on the circadian cycle. A daily dose of sunlight at specific times, such as waking up, for example, would improve sleep, melatonin secretion, the pupillary reflex, brain activity or even temperature and the cardiovascular system.
Therefore, it would be preferable for scientists to maintain winter time. “Sunset would take place on average 4 hours later in summer than in winter, instead of 3 hours with the current time change, and would induce an earlier bedtime and longer sleep which would be beneficial to our health “, assures Inserm.
To reduce the effects of the time change, the National Institute of Sleep and Vigilance recommends respecting your sleep rhythm, exposing yourself to daylight in the morning, practicing regular physical activity and favoring a quiet activity in the evening.
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Interview with Dr. Camille Dupont, Sleep and Circadian Rhythm Specialist at the National Institute of Sleep and Vigilance (INSV)
Editor: Good morning, Dr. Dupont. Thank you for joining us today. As many of our viewers know, France switched to winter time this past weekend, which brings about some physical and psychological implications. Could you briefly explain how this time change affects our biological clocks?
Dr. Dupont: Good morning! Yes, the switch to winter time disrupts our circadian rhythms, which regulate various bodily functions over a 24-hour cycle. When the clock falls back by an hour, it forces our body to adjust to a new schedule, which can lead to symptoms like sleep disturbances, fatigue, and changes in mood.
Editor: It sounds like these changes can have serious impacts. What are some specific health risks associated with the transition to winter time?
Dr. Dupont: Indeed, studies have shown that the time change can increase the likelihood of sleep disorders, fatigue, and even mood changes such as depressive symptoms. There’s also a documented rise in incidents like car accidents and myocardial infarctions shortly after the switch. Our bodies don’t always adapt smoothly to these sudden changes, which is why we see these results.
Editor: You mentioned that certain groups are more vulnerable to these effects. Could you elaborate on who might be most affected?
Dr. Dupont: Certainly. Children, the elderly, and individuals with sleep disorders are particularly susceptible to the negative effects. Additionally, night workers and teenagers may also experience pronounced disruptions. This is due to their varying lifestyles and biological needs which can make adjustments to time changes especially challenging.
Editor: It seems that switching to summer time is even harder on our biological clocks. Could you explain why that is?
Dr. Dupont: That’s correct. Transitioning to summer time means losing an hour of sleep, which can be more jarring. This, combined with a general lack of sleep reported among the French, exacerbates the issue. Our bodies already struggle to keep pace with our daily schedules, and having to advance the clock by an hour effectively increases that struggle.
Editor: There’s been discussion about potentially moving to permanent winter or summer time. What are the implications of this change?
Dr. Dupont: The idea of permanent time change is interesting. A consistent schedule could reduce the disruptions caused by seasonal changes, which may lead to improved overall health. However, it’s crucial to consider the varied preferences of the population. As mentioned, while a majority of Europeans favor permanent summer time, we must also weigh the biological impacts that such a shift may have.
Editor: Thank you, Dr. Dupont. Your insights shed light on the significant effects of this seemingly simple change. It’s clear that understanding our biological needs is essential for our health, especially during these transitions.
Dr. Dupont: Thank you for having me. It’s important for everyone to be aware of how time changes can affect us and to find ways to ease the transition for better health and well-being.
Editor: It seems that switching to summer time is even harder on our biological clocks. Could you explain why that is?
Dr. Dupont: That’s correct. Transitioning to summer time involves losing an hour of sleep as we set the clocks forward. This means our biological clock must adjust more significantly than with the transition to winter time. The abrupt shift can exacerbate existing sleep deficits, leading to higher levels of fatigue and a greater likelihood of mood disturbances. Essentially, during summer time, our bodies need to advance their internal clocks without enough recovery time, which often results in more pronounced negative effects.
Editor: Given these challenges, has there been any movement towards adopting a permanent time system, such as staying on winter time year-round?
Dr. Dupont: Yes, there’s been ongoing debate, especially in the EU, about whether to remain permanently on summer or winter time. While many citizens lean towards permanent summer time, scientific opinions suggest that maintaining winter time could adhere better to our biological needs. In winter, earlier sunrises align more closely with our natural wake times, potentially improving overall health and well-being.
Editor: what practical advice can you offer to help mitigate the negative impacts of the recent time change?
Dr. Dupont: To minimize the effects, it’s crucial to maintain a consistent sleep schedule as much as possible. Exposure to natural light, especially in the morning, is vital for resetting our circadian rhythms. Regular physical activity and winding down with calming activities in the evening can also help ease the transition. Lastly, listening to our bodies and allowing some flexibility during this adjustment period can make a significant difference in how we feel.
Editor: Thank you, Dr. Dupont, for sharing your insights. It’s always enlightening to hear from experts like you on how such changes affect our health.
Dr. Dupont: Thank you for having me! It’s important to keep the conversation going about our health and well-being.
