According to sleep specialists, adaptation is slower when the body is fragile.
The changeover to winter time takes place during the night of Saturday October 25 to Sunday October 26, 2025 in France. At 3 a.m., it will be 2 o’clock. We will therefore “gain” an hour of sleep. If this ritual initially aims to save energy, it is not without consequences for our biological clock, the famous circadian rhythm which governs our sleep, wakefulness and appetite cycles over 24 hours.
Although the majority of adults adapt within just a few days, some populations are much more sensitive to this one-hour delay. According to the observations of sleep specialists, adaptation is slower when the body is fragile. If the first night can be restful, the return to normal rhythm is gradual. “To absorb an hour of difference, it generally takes 3 or 4 days, but some people need 8 to 10 days to regain their balance.“, underlines Dr Catherine Lamblin, doctor specializing in sleep disorders.
Among the people for whom the time change is the most difficult to bear are “seniors”. It is generally from the age of 60-65 that the internal clock becomes less flexible. “Sleep becomes lighter, more easily fragmented and interrupted by frequent awakenings, making it more laborious to reset their rhythm“, confirm Dutch researchers in a study published in the journal Nature. This period of adjustment can manifest itself in fatigue, mood or appetite disorders. Infants and young children also represent a delicate group, because their sleep routine, so fragile, is very sensitive to jet lag.
The change to winter time is often easier to absorb than the change to summer time. The circadian rhythm is based in particular on the production of melatonin (the sleep hormone), which is strongly influenced by light. To adapt smoothly, expose yourself to natural light when going outside, especially in the middle of the day, and eat a light and early dinner to make it easier to fall asleep at the new time. You can also gradually shift your bedtime and wakeup time by 10-15 minutes a few days before.
