The intriguing German word zeitgeber arose during the research for the Naturopath’s Guide to Insomnia, which launched this month, so its meaning is investigated here. The term zeitgeber, which literally means time giver or time cue, was coined by chronobiologist Jürgen Aschoff in the 1950s. It refers to cues given by the environment that reset the circadian rhythm. The role of zeitgebers in the circadian rhythm is to make sure that the biological clock is synchronised with the individual's environment. Examples of the key zeitgebers in humans are environmental cues like light (considered the most important because it essentially indicates when to go to sleep and when to wake), physical activity, food intake, body temperature and social interaction. When and how these activities are done impacts the circadian rhythm and energy levels throughout the day. This means people have more control over their internal body clock than they think.
The insomnia guide says: “The regulation of sleep is processed by the circadian rhythm, the sleep/wake cycle. Circadian rhythm is the 24-hour internal clock in the brain that regulates cycles of alertness and sleepiness by responding to light changes in the environment. When properly aligned, a circadian rhythm can promote consistent and restorative sleep but when this circadian rhythm is thrown off, it can create significant sleeping problems, including insomnia.” As circadian problems often contribute to insomnia and daytime sleepiness understanding zeitgebers is a way to cue the body correctly and sync with nature to harness sleep and energy efficiently. When a person experiences significant changes in zeitgebers, such as during jetlag, these disruptions can lead to decreased cognitive performance, negative mood, and in some cases episodes of mental illness. Zeitgeber signals such as daylight, body temperature, meals and exercise schedules can be optimised to stabilise the internal clock.
Before electric lights were introduced about a century ago, people were exposed to minimal light at night. Exposure to unnatural light late into the night (especially from screens), and a lack of access to natural sunlight when working in an office, could contribute to difficulty sleeping. There is evidence that a drop in temperature helps to transition the body to sleep, such as by turning on a fan. Having a hot shower before bedtime can begin to balance the temperature causing a drop, and by sleeping with socks on the body will try to regulate by cooling the rest of the body. Eating at night can also affect how well a person sleeps. It is helpful to eat on some kind of schedule to give the body regular and reliable cues about when to expect energy, so it can use it most efficiently. Like the meal schedule, when a person exercises can also affect their sleep cycle. It is not so much about when they exercise, but more if the timing is consistent. The profound mismatch between the “enforced” sleep duration on school/work days and the variable sleep duration on days off demonstrates the strong effect of social times on daily sleep behaviour. The biggest take away is to be consistent in daily routines, be active and eat and drink during the daylight hours and when it’s dark outside go to sleep and don’t eat.
References
Pacheco D. Can You Change Your Circadian Rhythm? Sleep Foundation One Care Media c2023. (updated 18 Jan 2023; accessed 27 Jan 2023). Available from https://www.sleepfoundation.org/circadian-rhythm/can-you-change-your-circadian-rhythm
HEC The Naturopath’s Guide to Insomnia
Hussey KD. Rhythmic history: Towards a new research agenda for the history of health and medicine. Endeavour. 2022 Dec;46(4):100846. doi: 10.1016/j.endeavour.2022.100846. Epub 2022 Dec 13. PMID: 36521301.
Walker WH, Walton JC, DeVries AC et al. Circadian rhythm disruption and mental health. Transl Psychiatry. 2020;10(28). https://doi.org/10.1038/s41398-020-0694-0
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