Science

Full moon: what impact on your sleep?

Boosted plant growth, disruption of the female menstrual cycle, increased risk of natural disaster: since the dawn of time, humanity has lent a strong influence to the full moon, for better and for worse. And when it comes to our sleep, science has ruled: yes, the full moon disturbs it. Explanations.

The full moon is surrounded by a sulphurous reputation. Popular beliefs lend him powers that are as frightening as they are fascinating, which in particular gave rise to the myth of the werewolf. It has also long been criticized for disrupting sleep, and this was found to be scientifically correct at the dawn of the new millennium.

The moon’s impact on sleep: from legend to science

Between 2000 and 2003, researchers at the University of Basel, Switzerland, investigated the link between age and sleep quality. A group of 33 volunteers aged 20 to 74 were placed in an isolated environment and observed for 64 nights, distributed according to the lunar calendar. It was by chance, while chatting over a drink, that the team thought of observing a possible influence of the full moon.

By retrospectively analyzing various results – sleep structure, measurement of melatonin and cortisol secretion or even non-rapid eye movement (EEG) sleep electroencephalogram – they were able to establish that the deep sleep phases were shortened by 20 to 30% during full moon nights.

Although the explanation remains to be clarified, they then shed light on an astonishing fact: the rate of secretion of melatonin (the sleep hormone) was 50% lower than usual. Concretely, this translated into about 20 minutes less sleep in the study, and a 15% loss of sleep quality.

The effect of the full moon on sleep: confirmation

In 2020, it is the turn of researchers from the University of Washington (United States) to deliver their conclusions, and it is formal: during the full moon – and the 3 to 5 days preceding it -, falling asleep is delayed by 30 minutes on average, and sleep time shortens from 46 to 58 minutes. These data turn out to be the most precise so far, because they are not based on the feelings of the volunteers, but on measurements carried out thanks to various monitors.

3-5 days before a full moon night, study participants tended to sleep less and stay awake later. © L. Casiraghi et al.

American researchers favor a simple explanation: during the full moon, the satellite is fully exposed and it generously reflects sunlight. This luminosity disrupts the circadian rhythm on which our biological clock is based. However, the effects of light alone cannot fully explain the effect of the full moon on sleep. This study did indeed reveal a “semilunar effect”: variations in sleep occurring every two weeks – that is, halfway through the 29.5-day lunar cycle. Phenomena that are currently not understood should therefore not be ruled out.

How to fight against the effects of the full moon on sleep?

While the effects of the full moon on sleep retain their share of mystery, it is now established that they are very real. If you are sensitive to it yourself, there are a few tips that can help you sleep better during these times.

To take full advantage of the deep sleep phases, although they are shorter, and to limit the risk of waking up unexpectedly, try to start by limiting the exposure of your sleeping environment to moonlight as much as possible. It is also essential to have good bedding. The new generation mattresses now offer appreciable comfort, but to get the most out of them, it is also recommended to use a pillow adapted to your morphology and your preferred sleeping position.

During the full moon phases, more than ever, it is important to ensure a healthy lifestyle, avoiding an overly large dinner. Also, be sure to ban alcohol in the evening, and limit your intake of exciting substances, such as coffee. Finally, avoid screens the hours before bedtime, whose blue light very similar to that emitted by the sun contributes to disrupting the circadian rhythm! Prefer a quiet activity, such as reading or meditating.

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