The sleep-hormone connection.

What Summer Disrupts — and How to Protect It

There is a particular kind of exhaustion that arrives in summer — not from overwork or illness, but from nights that somehow never quite restore you. You fall asleep easily enough. But then 4am arrives with its pale light and birdsong, and that's it. The night is over whether you wanted it to be or not.

If this sounds familiar, your hormones are almost certainly involved.

Summer creates a set of conditions that quietly work against the hormonal balance your sleep depends on — more light, more heat, later evenings, disrupted routines. Understanding what is happening beneath the surface is the first step to doing something about it.

The Sleep-Hormone Connection

The Hormones at the Heart of Your Sleep

Melatonin — Your Darkness Signal

Melatonin is produced by the pineal gland in response to darkness. It doesn't make you sleep — it signals to your body that night has arrived and that sleep is appropriate. In winter, with darkness falling early, this signal comes reliably and early. In summer, it doesn't.

Long evenings, bright screens, and the ambient light of midsummer all suppress melatonin production and push its release later into the night. The result is that your body simply doesn't receive the “it's time” signal at the hour it needs to.

For women in perimenopause and beyond, this is compounded by the fact that melatonin production naturally declines with age — meaning the signal was already quieter before summer made it quieter still.

Cortisol — Your Waking Hormone

Cortisol follows a natural rhythm: high in the morning to wake you, gradually declining through the day, low at night to allow sleep. Summer disrupts this in two directions.

First, early light triggers cortisol release earlier than your body expects — which is why you might find yourself suddenly, completely awake at 5am in July even when you went to bed late. Second, heat raises cortisol. A warm bedroom, a warm body, a night without airflow — all of these keep cortisol slightly elevated when it should be falling, making it harder to reach the deep, restorative sleep stages your brain and body need.

Serotonin — The Bridge Between Gut and Sleep

Serotonin is often framed as a mood hormone, but its relationship with sleep is more fundamental than that. Melatonin is synthesised from serotonin — you cannot make one without the other. Which means that anything disrupting your serotonin levels will also quietly disrupt your sleep.

Here is the part that most people don't know: approximately 90% of the body's serotonin is produced not in the brain, but in the gut. This is why gut health and sleep quality are so deeply intertwined. A digestive system that is inflamed, imbalanced, or poorly nourished will produce less serotonin — and less serotonin means less melatonin, which means poorer, less restorative sleep.

In summer, eating patterns often shift — more alcohol, more irregular mealtimes, more processed food at barbecues and holidays. The gut notices. Supporting your gut microbiome is, in this very real sense, supporting your sleep.

Oestrogen — Temperature, Mood, and the Night

Oestrogen plays a significant role in thermoregulation — the body's ability to maintain a stable core temperature. It also supports serotonin production and modulates the stress response, making it a quiet but powerful regulator of how easily the nervous system settles at night.

When oestrogen levels are fluctuating or declining — as they do in perimenopause — thermoregulation becomes less reliable. Night sweats and hot flushes are the most visible symptom of this. But even without dramatic sweating, a subtly dysregulated body temperature in the night can prevent the deep sleep stages the brain needs to consolidate memory and carry out its essential repair work.

In summer, when the ambient temperature is already higher, this becomes more pronounced. The body is working harder to cool itself just at the point when it needs to be doing the opposite. A cool bedroom becomes less of a preference and more of a necessity.

Progesterone — The Often Overlooked Piece

Progesterone has a natural calming, sedative effect on the nervous system. It supports GABA — the brain's primary inhibitory neurotransmitter — and plays a significant role in sleep quality, particularly in the second half of the night.

For women in their 40s and 50s, progesterone levels are declining. This means less natural sedation, lighter sleep, more waking in the early hours, and a nervous system that is simply less buffered against disruption. Summer's additional stressors — heat, light, irregular routines — land on a foundation that is already less stable than it once was.

Leptin and Ghrelin — When Sleep and Appetite Converge

Leptin and ghrelin are the hormones that regulate hunger and satiety. Leptin signals fullness; ghrelin signals hunger. What most people don't realise is that both are directly regulated by sleep — and that poor sleep disrupts both within a single night.

When sleep is fragmented or shortened, leptin levels drop and ghrelin rises. The result is increased appetite the following day — particularly for carbohydrate-dense and calorie-dense foods — not from lack of willpower, but from a hormonal shift that is actively driving the craving. This is one of the reasons poor sleep and weight gain are so consistently linked in the research.

This also works in the other direction: eating a heavy meal close to bedtime raises blood sugar and keeps the digestive system active, which makes it harder to reach deep sleep — which then disrupts leptin and ghrelin the next day. Finishing your evening meal two to three hours before bed gives the body a genuine chance to shift into the digestive rest it needs before sleep begins.

Sleep is not governed by a single hormone. It is the result of a beautifully coordinated conversation between the brain, nervous system, hormones, metabolism, and our environment.

If you have specific concerns about hormonal testing, diagnosis, HRT, or progesterone levels, please speak with your GP or an endocrinologist — these are clinical conversations that need clinical care.

If you'd like to explore the nutrition, gut & brain health, hormonal wellbeing, sleep hygiene, and nervous system regulation side of this, that's exactly what I work on with women. I'd love to talk — julia@neurowellness.one

What I Do Personally to Protect My Sleep in Summer

I want to share what actually works for me — not as prescription, but as a starting point for your own experimentation. Everyone's nervous system is different, and what I've arrived at has taken years of adjustment and honest observation.

No coffee after 4pm. Caffeine has a half-life of approximately five to six hours, meaning half of a 4pm coffee is still active in your system at 9–10pm. For those of us who are slower caffeine metabolisers — which is more common than people realise — the effect lasts even longer. I moved my last coffee earlier and the difference in how easily I transition into evening was immediate.

A window open during the night. Core body temperature needs to drop by approximately one degree for deep sleep to occur. A cool bedroom — ideally between 16 and 19 degrees — supports this process. Fresh air also shifts the quality of sleep in a way that's difficult to quantify but very easy to feel.

A cool shower before bed, focusing on the legs. Cold water on the legs in particular helps dissipate heat from the body rapidly and has a genuinely calming effect on the nervous system. This has become non-negotiable for me in summer.

An evening walk if possible. Gentle movement after dinner supports digestion, helps cortisol finish its natural decline, and creates a clear boundary between the activity of the day and the stillness of the evening. Even fifteen minutes makes a difference.

A soothing herbal tea. Chamomile, fennel, fresh mint from the garden, rooibos — these are not just comforting rituals. Many have mild nervine properties that genuinely support the transition into rest. They also replace the habit of reaching for something stimulating in the evening.

No phone in the bedroom. Not on silent. Not face down. Not there. The blue light suppresses melatonin, but that's almost secondary. The deeper issue is that the nervous system cannot fully downregulate when it knows a device is present that might demand something of it. The bedroom needs to be a space the body associates entirely with rest.

Magnesium glycinate before bed. Magnesium plays a direct role in nervous system calming — it supports GABA activity, helps regulate cortisol, and promotes the muscular relaxation the body needs to move into deep sleep. It is one of the most well-researched supplements for sleep quality and one I return to consistently, particularly through summer when sleep is more disrupted.

Reishi tincture in the evening. I also take a few drops of Reishi tincture in the evening. Reishi is an adaptogenic mushroom — one of the most revered in traditional Chinese medicine — known for its ability to calm the nervous system, support the body's stress response, and gently quiet the mind before sleep. It is not a sedative; it works more subtly than that. Used consistently, I notice the difference.

Practitioner-supported hormonal care. I also work with a practitioner-prescribed supplement to support my progesterone levels. I am not sharing the specifics here intentionally — hormonal support is highly individual, and what is right for one person's biochemistry may not be appropriate for another's, particularly for those on HRT or other medication. If this is an area you are navigating, please work with a qualified practitioner who can assess your individual picture.

A word about perimenopause

If you are in your 40s or 50s and your sleep has changed in the last few years — becoming lighter, more fragmented, or simply less restorative — I want you to know that this is one of the most commonly reported and least discussed aspects of the perimenopause transition.

Declining progesterone and oestrogen directly affect sleep architecture. Night sweats raise core temperature at precisely the wrong moment. Cortisol becomes more reactive. And the nervous system, without adequate hormonal buffering, is simply more sensitive to disruption.

The nervous system responds to support — not by fighting your biology, but by working with it.

Somatic practices, breathwork, nutrition, sleep hygiene, and targeted lifestyle adjustments can all make a meaningful difference.

Where to begin

If your sleep has felt off this summer, start with one thing from the list above. Not all of them — one. Notice what shifts over a week. Then add another.

And if you'd like more personalised support — whether that's understanding your own hormonal picture, building a nervous system routine that actually fits your life, or working through what's keeping you from restorative sleep — I'd love to talk.

Coming up at neurowellness.one

Join me for Rest, Regulate, Restore — a nourishing day at Tofte Manor on 23 September. We will begin with gentle somatic yoga, share a gut-brain nourishing lunch, drift into a healing sound bath, and close with a special talk from Sophie Barrett on Women's Health & Medicinal Mushrooms, exploring how Reishi, Shiitake and other fungi support hormonal balance and nervous system resilience through every stage of life. Find out more and book your place →

Restorative Immersion

Friday 14th August. A 90-minute restorative practice designed to prepare the body and nervous system for deep, quality sleep. If the sleep theme here resonated with you, this is the natural next step. Book your place via Momoyoga →

Working with me 1:1

If you are ready for personalised support — sleep, nervous system regulation, nutrition — I am currently offering 10% off all new 1:1 programmes. Book a free discovery call →

Summer offer — 10% off the 12-Week NeuroWellness Return. A personalised, evidence-informed programme built around your nervous system, your hormones, and your life.