It’s 2 a.m. You wake up drenched, kick off the covers, and lie there wondering what on earth your body is doing. Or it’s the middle of a meeting, and a wave of heat rises through your chest and face while everyone else seems perfectly comfortable.
Hot flushes are one of the most common experiences during the menopause transition. Research suggests that up to 80% of women experience them at some point during perimenopause and menopause.
But why do they happen? Why can a tiny change in body temperature trigger such an intense reaction? And what does falling oestrogen have to do with it?
The answer begins in your brain.
Your body isn't necessarily overheating
A hot flush feels like your temperature has shot up. In reality, it’s better understood as a cooling response that your brain switches on when it doesn’t need to.
It's an exaggerated response from your body's temperature-regulation system, even though the change in your core body temperature may be very small.
Blood vessels close to the skin widen, allowing more blood to flow near the surface. This causes the familiar redness and feeling of heat. Your sweat glands become active, too, as your body attempts to cool itself down.
Some women feel their heart beating faster. Others experience dizziness, anxiety or a chill once the sweating subsides.
To understand why this happens, we need to look at a part of the brain most of us rarely think about.
Meet your brain's thermostat
Deep inside your brain is a small region called the hypothalamus. Among its many jobs is helping regulate your body temperature, keeping it within a range where your body can function comfortably.
Scientists call this range the thermoneutral zone.
Within this zone, your body doesn't need to take major action to warm up or cool down. If your temperature falls too far, you may shiver. If it rises too far, you sweat to release heat.
During the menopause transition, this temperature-regulation system can become more sensitive. The thermoneutral zone is thought to narrow, meaning even a small change in core body temperature can trigger a cooling response.
Think of a smoke alarm that has become so sensitive it goes off when you make toast. Nothing is on fire. The sensor is simply reacting to something it used to ignore.
So why does this happen during perimenopause and menopause?
What does oestrogen have to do with it?
Oestrogen plays a role in regulating several systems throughout the body, including the brain pathways involved in temperature control.
During perimenopause, oestrogen levels can fluctuate considerably. As the transition progresses, levels generally decline. These hormonal changes are thought to affect the brain's ability to regulate body temperature.
Researchers have identified a group of nerve cells in the hypothalamus known as KNDy neurons. The name comes from three chemical messengers these cells produce: kisspeptin, neurokinin B and dynorphin.
These neurons help coordinate reproductive hormone signalling and are also involved in temperature regulation.
Oestrogen normally influences how these neurons function. When oestrogen levels change, their activity and signalling can change, too. In particular, neurokinin B signalling plays an important role in triggering the pathways involved in hot flushes.
This is a leading explanation for why hot flushes occur, although researchers are still working to understand the full picture.
It is also an important development in women's health research. A better understanding of these brain pathways has helped researchers develop non-hormonal medicines that target neurokinin signalling to reduce hot flushes.
In other words, hot flushes involve a complex interaction between hormonal changes and the brain's temperature-regulation system. And no, they're not something you can necessarily control by trying harder to stay calm or cool.
Why do hot flushes happen at night?
For some women, hot flushes happen frequently at night. These are known as night sweats.
You might be wondering: why does this happen when I'm asleep, even when my bedroom temperature hasn't changed? Why am I suddenly waking up hot and sweaty when I was perfectly comfortable just moments before?
Part of the answer lies in your body's natural temperature rhythm.
Your core body temperature doesn't remain constant throughout the day. It gradually falls in the evening, reaches its lowest point during the night, and begins to rise again towards morning. This daily rhythm is closely connected to your sleep-wake cycle, with your brain continuously adjusting how your body releases and retains heat.
During the menopause transition, this normal temperature-regulation rhythm can interact with the hormonal changes we've discussed above, making night-time hot flushes more likely for some women.
Researchers are still working to understand exactly how hormonal changes, circadian rhythms and sleep interact to influence night sweats. What we do know is that when these episodes repeatedly wake you, the effects can go well beyond feeling hot. Broken sleep can leave you tired, foggy and less able to cope with the demands of the following day.
It’s a whole-body system, not just “hormones”
The hypothalamus is more than a thermostat. It’s a hub that connects your reproductive hormones (the HPO axis), your stress response (the HPA axis), your sleep and your nervous system. That’s one reason symptoms rarely arrive alone, and why hot flushes, sleep, mood and energy can all feel tangled together.
Research also shows that women who report higher stress, anxiety or low mood when symptoms begin tend to have symptoms that last longer. That is an association. It does not mean stress causes hot flushes, and it certainly doesn’t mean you’re doing anything wrong. It simply points to why looking after the whole system matters.
Read our ecosystem blog to learn how these systems interact and shape the way women experience the hormonal and menopause transition.
How long will hot flushes last?
This is often one of the first questions women ask, and understandably so.
The answer is that it varies considerably from woman to woman.
In the long-running US Study of Women's Health Across the Nation (SWAN), researchers found that frequent hot flushes and night sweats lasted a median of about 7.4 years. For women whose symptoms began before their final menstrual period, the median duration was longer.
A median is the midpoint of the observed durations. Some women experience symptoms for a much shorter time; others experience them for considerably longer.
This also means the old expectation that hot flushes will disappear within a year or two doesn't reflect everyone's experience.
If symptoms are affecting your sleep, work or quality of life, you don't have to wait for them to pass before seeking help.
What can help with hot flushes?
There isn't one approach that works for every woman. What helps depends on the severity of your symptoms, your health, your preferences and how much the symptoms are affecting your life.
Here are some practical starting points.
1. Make it easier to cool down
Lightweight, breathable clothing, removable layers, a fan and a cool bedroom can make flushes more manageable. Try lighter or layered bedding so you can adjust it easily during the night.
2. Notice your personal triggers
Some women notice that alcohol, caffeine, spicy food, warm environments or stressful situations coincide with their flushes. Others find no consistent pattern.
Rather than cutting out everything at once, keep a simple diary for a couple of weeks. Note when flushes happen, what you were doing, what you had eaten or drunk, and how you slept. You may identify a pattern that is useful to you.
3. Consider evidence-based psychological approaches
Menopause-specific cognitive behavioural therapy (CBT) can help women manage the impact of hot flushes and night sweats, including associated sleep difficulties and distress. Clinical hypnosis is another approach supported by some clinical guidelines.
These approaches may not eliminate every flush, but they can help reduce how disruptive symptoms feel and improve quality of life.
4. Talk to your healthcare professional about treatment
If hot flushes are affecting your life, there are treatment options worth discussing.
Menopausal hormone therapy (MHT), also called hormone replacement therapy (HRT), is the most effective medical treatment for hot flushes and night sweats for many women. Whether it's appropriate depends on your medical history, individual risks, preferences and stage of life.
Non-hormonal prescription treatments are also available, including options that target the brain pathways involved in hot flushes.
You don't need to wait until symptoms become unbearable to ask for help. A GP or suitably qualified menopause practitioner can discuss the benefits, risks and alternatives relevant to you.
5. Support your health beyond the hot flush
Food, gut health, movement, stress and sleep all interact with how you feel through midlife. The research on specific foods and supplements for hot flushes is mixed and varies from person to person, so be wary of anything that promises a quick fix.
Key takeaways
- Hot flushes are a cooling response triggered by your brain’s thermostat, not a sign your body is truly overheating.
- Falling oestrogen is thought to narrow your comfortable temperature range, so small changes can set off the response.
- Night sweats are hot flushes during sleep, and sleep disruption deserves attention in its own right.
- Duration varies widely. Many women experience symptoms for longer than a year or two, and support is available.
- You have options, so don't wait until the symptoms become unbearable.
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Frequently asked questions
What causes hot flushes during menopause?
Hot flushes are triggered by your brain’s thermostat, not by your body genuinely overheating. As oestrogen falls and fluctuates, your comfortable temperature range is thought to narrow, so a tiny rise in core temperature can set off flushing and sweating. Researchers believe overactive KNDy neurons in the hypothalamus play a key role.
What is the difference between hot flushes and night sweats?
There is no difference in the mechanism: night sweats are hot flushes that happen while you sleep. They can wake you, dampen your sleepwear and bedding, and leave you chilly afterwards, which is why they often disrupt sleep more than daytime flushes.
Why do I feel cold after a hot flush?
During a flush, widened blood vessels and sweating release heat. Unlike a fever, your core temperature actually drops, so many women feel chilly or shivery once the flush passes.
How long does a hot flush last?
Most last from under a minute to a few minutes. How often they happen and how intense they feel varies widely between women, and even from day to day.
How many years do hot flushes and night sweats last?
In the large SWAN study, frequent hot flushes and night sweats lasted a median of 7.4 years. That ranged from around 5 years in some groups of women to 10 years or more in others, and symptoms that began earlier in the transition tended to last longer.
When do hot flushes start?
They can begin in perimenopause, sometimes before your periods change at all. In one review, about 31% of women noticed hot flushes before any change in their menstrual cycle.
What triggers hot flushes?
Many women notice triggers such as warm rooms, alcohol, caffeine, spicy food and stress. Research on avoiding triggers to reduce hot flushes is limited, so treat it as personal detective work. A short symptom diary can help you spot what sets yours off.
Can stress make hot flushes worse?
Women who report more stress, anxiety or low mood when symptoms begin tend to have symptoms that last longer. That is an association, not proof that stress causes hot flushes. Calming and coping strategies can still help with how you experience them.
Are hot flushes a sign of heart problems?
Not on their own. Severe hot flushes are associated with some cardiovascular risk factors, such as high blood pressure and cholesterol, but in a large study of women, hot flushes in early menopause were not linked to heart attack or stroke. Experts caution against alarm, because the associations often aren’t independent of other risk factors. Midlife is simply a good time for a heart-health check.
Do hot flushes affect sleep and mood?
They can. In a study of nearly 50,000 women, sleep disturbance was linked to lower quality of life, anxiety and low mood, even among women without hot flushes. If your sleep or mood is struggling, that is worth raising with your doctor in its own right.
What can help with hot flushes and night sweats?
Cognitive behavioural therapy (CBT) designed for menopause and clinical hypnosis are both recommended in the 2023 Menopause Society position statement on non-hormone therapy. Menopausal hormone therapy is an effective medical treatment for many women, and non-hormonal and natural options exist too. Cooling strategies such as layers, light bedding and a cool bedroom are helpful for comfort, though they haven’t been shown to reduce how often flushes happen.
Does HRT help hot flushes?
Yes. Menopausal hormone therapy is an effective medical treatment for hot flushes and night sweats, but it isn’t suitable for everyone, for example women with a personal history of breast cancer, stroke or blood clots. A GP or menopause specialist can help you weigh up the benefits and risks for you.
Are there non-hormonal treatments for hot flushes?
Yes. Besides CBT and clinical hypnosis, some prescription medicines such as certain antidepressants and gabapentin are used for hot flushes, and a newer medicine called fezolinetant targets the brain pathway involved. The UK’s NICE has recommended fezolinetant for women who can’t or prefer not to use HRT. Ask your doctor what is available and funded in New Zealand.
Do supplements help hot flushes?
The evidence is mixed, and results can vary considerably depending on the ingredients and the product. The source and quality of an ingredient, how it is extracted and standardised, the dosage, the overall formulation and how the active compounds are delivered can all influence what a product provides. Just as importantly, research findings for one ingredient or formulation may not apply to another. Look beyond the marketing claims. Check whether the specific ingredients and dosages are supported by credible scientific research, and whether clinical studies have tested the actual ingredient/active compound.
Can men get hot flushes?
Yes. Men with low testosterone, including those having treatment for prostate cancer, can get hot flushes through the same temperature-control pathway.
Why is the body’s thermostat connected to reproductive hormones?
The leading idea is that reproduction is energy-hungry and sensitive to body temperature, so the same hypothalamic neurons that read oestrogen and energy status also influence temperature. This keeps fertility, energy and warmth coordinated. When oestrogen declines, that link can produce hot flushes. It is a well-supported hypothesis rather than a proven explanation.
When should I see a doctor about hot flushes or night sweats?
See your doctor if hot flushes or night sweats are disrupting your sleep, mood or daily life, if they start before the age of 45, or if you have unexpected bleeding. Night sweats can also have other causes, such as infections, thyroid conditions or some medicines, so get them checked if they feel unusual or come with fever or unexplained weight loss.
Is it “hot flush” or “hot flash”?
They mean the same thing. “Hot flush” is the usual term in New Zealand, Australia and the UK, and “hot flash” is more common in the US.
Disclaimer - This content is for general informational purposes only and is not intended to imply benefits of any specific product.