What impact do hormones have on sleep?

There are several hormones that have a direct or indirect influence on the quality and quantity of our sleep. We have grouped these different hormones. These chemical messengers perfectly orchestrate the body's various functions, including our sleep.

From the circadian rhythm through to stress, key sleep hormones such as melatonin, cortisol and others have a considerable impact on our period of night-time rest. We have studied these different hormones in order to better guide you through their roles and help you better understand your nights and what can facilitate good sleep quality and easy sleep onset.

Melatonin, sometimes called the “sleep hormone”, is produced by the pineal gland, nestled in the centre of the brain. Derived from tryptophan, an amino acid, it helps your body naturally prepare for falling asleep. Peak melatonin levels are reached at around 2 a.m.

Factors influencing melatonin production:

• Light exposure: Too much light, especially blue light from electronic screens, can inhibit its secretion.
• Age: Production naturally decreases with age, which can explain sleep disorders in older people.
• Diet: Certain foods such as cherries, nuts and milk contain melatonin.

Melatonin production follows a circadian rhythm, meaning it increases in response to the decrease in daylight. At the end of the day, melatonin secretion begins, preparing the body for sleep. Conversely, morning light inhibits its production, promoting waking.

This hormone has a direct impact on sleep quality. An adequate level of melatonin leads to faster sleep onset and improves sleep depth. Studies show that disturbances in its production can lead to insomnia or irregular sleep.

Cortisol is recognised as the main stress hormone and plays a key role in our sleep–wake cycle. It is secreted by the adrenal glands; its level peaks early in the morning to wake us up and decreases throughout the day to reach its lowest point at night.

Cortisol dysregulation affects sleep quality. Chronic stress can also stimulate its production, disrupting sleep and making it harder to fall asleep.

Adenosine is another important chemical messenger. It contributes to the feeling of sleepiness. As we stay awake, its level rises, promoting fatigue and preparing the body for sleep. The opposite process takes place during the night to help us feel alert in the morning.

As we stay awake, adenosine accumulates in our brain, increasing sleep pressure. When its levels are high enough, it promotes the urge to sleep. During sleep, its concentrations decrease, lowering this pressure and making it easier to wake up in the morning.

Caffeine, found in coffee and certain teas, blocks adenosine receptors, thereby delaying sleepiness. Difficulty falling asleep can appear when you consume caffeine too late in the day.

Both men and women produce sex hormones that strongly influence sleep patterns. These effects can vary depending on the specific hormonal cycles of each sex.

Fluctuations in estrogens and progesterone during the menstrual cycle can affect sleep quality. During the luteal phase (after ovulation), progesterone levels rise, which often has a sedative effect. Some women also experience worsening insomnia symptoms and poorer sleep quality during premenstrual syndrome (PMS)

• Pregnancy: High levels of hormones such as progesterone can trigger excessive sleep at the beginning and worsen insomnia in the third trimester.
• Menopause: Sudden drops in estrogens and progesterone can cause hot flushes and night sweats, interrupting sleep.

Although less often discussed, the gradual decline in testosterone in older men can also affect sleep. Lower levels of this hormone have been linked to reduced sleep quality and disorders such as obstructive sleep apnoea.

Menstrual cycles change estrogen and progesterone levels, thereby affecting sleep. Before menstruation, a drop in progesterone can lead to difficulty falling asleep or insomnia.

During pregnancy, progesterone and relaxin levels also rise, causing sleep disturbances. The frequency of night-time awakenings often increases due to physical discomfort and the ongoing needs of the foetus.

Menopause leads to a significant reduction in estrogen levels. This can bring on symptoms such as night-time hot flushes and sweating, disrupting sleep. In addition, the age-related drop in melatonin further complicates the situation.

By adjusting your lifestyle and habits, you can improve the regulation of your sleep hormones and promote more restorative, higher-quality rest.

• Adopt a regular sleep routine: Going to bed and getting up at the same time every day helps regulate your body clock.

• Reduce evening exposure to blue light: Use blue-light filters on your devices or build screen-free habits before bedtime.

• Manage stress: Incorporate relaxation techniques such as meditation, deep breathing or yoga to lower cortisol levels.

• Do moderate physical activity: Favour exercise during the day to avoid excessive stimulation in the evening. Regular exercise can effectively regulate certain sleep hormones such as adenosine and cortisol. Moderate physical activity not only improves total sleep time but also reduces anxiety and stress, contributing to better hormonal regulation.

• Avoid stimulants before bedtime: Limit caffeine and heavy meals to create an environment favourable to melatonin production. By contrast, foods rich in tryptophan such as turkey and pulses help produce melatonin.

Various factors influence how hormones affect our sleep, creating variability between individuals.

• Age: Hormone levels change with age, thereby altering sleep needs.
• Sex: As discussed, sex strongly influences hormonal variations and their effects.
• Lifestyle: Stress, diet and exercise can all alter hormone levels.
• Genetics: Some individuals may be naturally predisposed to hormonal imbalance.

Looking at screens in the evening can delay melatonin secretion, as blue light has an inhibitory effect. In contrast, sufficient exposure to natural light during the day strengthens its release at night.

Taking melatonin (1 to 2 mg, about an hour before bedtime) can be useful for people over 55 with primary insomnia or to ease jet lag. Do not exceed 2 mg per night without medical advice. Certain situations (pregnancy, epilepsy, specific treatments) require the opinion of a healthcare professional.

Plants such as valerian, chamomile and lavender have traditionally been used to promote sleep by reducing anxiety and balancing the hormonal system. In addition, minerals and vitamins such as magnesium and vitamin B6 also play a crucial role in supporting the natural production of melatonin and regulating cortisol.