Changing the clock time, circadian rhythms and sleep – GIMM Changing the clock time, circadian rhythms and sleep – GIMM

  October 30, 2024

Changing the clock time, circadian rhythms and sleep

Last weekend we altered our clocks back from the daylight saving time. What is the scientific opinion on this topic? We asked Cátia Reis, chronobiologist and somnologist from Luísa Lopes Lab, to share her opinion with us.




“Circadian rhythms are biological rhythms with a duration of approximately 24 hours, i.e. about one day, which is why they are called circadian rhythms. These rhythms are endogenous, have a genetic origin, function even in the absence of external cues, but synchronize with external cues. The primary synchronizer of our biological rhythms is the light stimulus, and light is just as important as its absence for proper synchronization of the day/night cycle. In other words, our biological clock is synchronized by the solar clock. 

Our circadian rhythms, which are synchronized by light, modulate our physiology, from metabolism to behavior. The fundamental and most easily perceived behavioral circadian rhythm is the sleep/wake rhythm. The sleep/wake rhythm is, however, accompanied by other biological rhythms, also with circadian variation, such as temperature, the production of certain hormones such as melatonin, cortisol or testosterone. All these rhythms vary in a cyclical and concerted way, providing a good sleep but most of all a good vigilance. This synchronization is optimal when solar time closely aligns with the biological clock. 

Several countries, including Portugal, adopt a change in social time during the spring and fall periods. This change is the artificial advancement of the social clock by 1 hour that occurs after spring, returning to standard time in the fall period, which occurred last weekend (2 a.m. became 1 a.m. according to social/clock time). Throughout the year the days are naturally shorter in winter, growing longer as spring approaches, and over the centuries organisms have adapted to this annual variation in light exposure by synchronizing with it. This artificial advance of social time in the spring period leads to a misalignment between solar time and biological time. While your bedtime remains consistent, as dictated by the biological clock, the time you wake up is shifted earlier to align with the social clock. This adjustment reduces total sleep time during this period, particularly affecting those with later sleep and wake patterns, and may persist throughout the summer. Such shifts can lead to acute sleep deprivation during the initial transition, and potentially chronic sleep deprivation across the summer months, heightening susceptibility to health issues. In recent years we have witnessed the discussion of the time change, where this issue has been widely debated. The scientific community has drawn attention to the importance of synchronizing biological rhythms to solar time and, as such, maintaining standard clock time throughout the year. Thus, maintaining the best possible alignment between these clocks (biological, solar and social). 


Having said that, I can only say… do outdoor activities for better synchronization and take care of your sleep, it’s fundamental to ensure good wakefulness!”



Cátia Reis 

5 5 votes
Article Rating
Subscribe
Notify of
guest
0 Comments
Inline Feedbacks
View all comments
0
Would love your thoughts, please comment.x
()
x