YOUR BRAIN ON MENOPAUSE: In this seven-part series, I explore menopause from a brain health perspective with a particular focus on the neurobiology of hot flashes, sleep, mood and memory, the role of hormone therapies and their long-term effects on the brain. This is Part 4.
When I was writing my book on women’s brain health (and being in my relatively inexperienced early 40s) I asked my older wiser bookclub friends what they struggled with most during their menopause transition. They all responded loudly with one word: SLEEP!
Now, I love to sleep. I powernap most days and usually head off to bed around 9 p.m. with a good book. Not a lot gets between my pillow and me (just ask my husband). So the prospect of disrupted sleep made me very nervous about the decade ahead.
Poor sleep and menopause: perfect bed partners.
A search of the literature supports the experiences of my book club. Forty to sixty per cent of women going through the menopausal transition report problems with sleep. The most common complaint is waking up at night for no apparent reason, followed by trouble falling asleep.
No aspect of our biology is safe from sleep loss!
Skip one night’s sleep and you feel utterly dreadful. Regularly get insufficient sleep or work the night shift and you’re at risk of depression, metabolic disorders such as Type 2 diabetes, cardiovascular disease, cognitive decline and a host of other health problems including increased mortality.
One in three perimenopausal women says sleep problems cause them distress and impacts their daytime functioning, which pretty much qualifies them for a diagnosis of insomnia. If left untreated, insomnia is associated with a number of adverse health outcomes.
Curiously, in women but not men, sex hormones partially regulate sleep. This may explain why sleep disruptions strike often strike during times of hormonal transition such as puberty, pregnancy and menopause, and during various stages of the menstrual cycle.
A quick guide to the neurobiology of sleep
Like all creatures, we evolved internal biological clocks that are synchronised by the rising and setting of the sun. Our biological clocks determine daily rhythms including when we fall asleep and wake up.
Information about night and day is relayed from our eyes via the optic nerve to our master circadian clock — the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN is rich with receptors for oestrogen and forms circuits with other brain regions involved in arousal and attention. Melatonin, a sleep hormone released from the pineal gland, is stimulated by darkness and inhibited by light. Melatonin works in partnership with the SCN to regulate sleep.
Over the course of a night we pass through a number of sleep stages. We typically cycle from stage one (relaxation) through to four (deep restorative sleep) and back again to REM (rapid eye movement/dreaming) sleep. One ‘sleep cycle’ takes about ninety minutes. The term sleep architecture describes the various cycles and stages you move through during the night.
Sleep and body temperature are intimately connected
Until we start to go through menopause, many of us are unaware that sleep and body temperature are intimately connected.
Like all body systems, our core body temperature follows a 24-hour circadian cycle. Core temperature is the lowest overnight, with sleep onset triggered as body temperature starts to decline in the evening. Indeed, one key role for the sleep hormone melatonin is to regulate the drop in core body temperature. And the decline is achieved via vasodilation, and thus heat loss, from your hands and feet.
This is one reason why having a hot shower or taking a hot water bottle to bed for your feet helps you fall asleep: Heat triggers dilation of blood vessels and speeds up heat loss, thus hastening the onset of sleep.
It goes without saying that hot flashes and night sweats are an obvious reason why women going through menopause wake up at night. But, not every woman wakes up during a nighttime flash.
Indeed, you do not need to be woken for higher core body temperature to disrupt sleep architecture. Even minor variations in core temperature disrupt both deep slow-wave sleep and REM sleep. The natural consequence of sleep architecture disruption is women feeling tired, foggy, grumpy and confused.
In her excellent book ‘The Menopause Manifesto’, OBGYN Dr Jen Gunter notes,
Medically what is happening is best described as an excessive arousal, meaning the sleep is just not as deep as it should be, and much of this may be due to hot flushes. In other words, for some women hot flushes are enough to disturb how deep they sleep but not enough to wake them up.Jen Gunter, The Menopause Manifesto.
For many women going through menopause, a domino effect of sorts may be at play: dysregulated hormones > disrupted hypothalamic thermoregulation > disrupted sleep architecture > tiredness / brain fog / forgetfulness/ mental health problems etc.
Are you too hot to sleep?
Leaving menopause aside for a moment, heatwaves, for example, are known to fragment sleep architecture, leaving even the young, fit and male reporting restless sleep with negative effects on next-day mood and alertness.
Most of us have had the experience of finding it harder to sleep when our bedroom is too hot. In short, you don’t cool down as easily, so it takes longer to fall asleep.
Writing for The Conversation, Professor Ron Grunstein from the University of Sydney explains that a room temperature of 22˚ or 23˚ Celsius is ideal.
Any major variation in this leads to disturbance of sleep with reduced slow wave sleep (a stage of sleep where the brain’s electrical wave activity slows and the brain “rests”), and also results in less dreaming sleep (rapid eye movement or REM sleep).
In theory, it may also have subtle effects such as problems with complex memory retention, higher judgement (poorer decision making and increased risk-taking behaviour), blood pressure control and regulation of glucose in the body.Ron Grunstein, Professor of Sleep Medicine. The Conversation
Does hormone therapy help sleep?
As we’ve discussed previously, hormone therapy is the most effective treatment for women suffering hot flashes or night sweats.
The Australian Menopause Society states,
“The use of oestrogen, alone or in combination with a progestogen, has been shown to improve the subjective quality of sleep.
Women with hot flushes treated with menopausal hormone therapy (MHT) show a marked improvement in sleep quality.”Australian Menopause Society
However, not all women find HRT helps their insomnia. This is because there are plenty of reasons for developing sleep problems at any point in the lifespan.
A combination of stress, poor lifestyle choices, medical conditions, or plain old bad habits such as taking your iPhone to bed for a late evening scroll impacts healthy sleep.
Midlife also brings with it difficulties with work, teenage children (perhaps even a child going through puberty) potential problems with long-term relationships, ageing parents and the occasional global pandemic.
We know poor sleep affects mood the next day and feeling anxious in turn adversely affects sleep. The vicious cycle of insomnia and anxiety is well-established.
Still can’t sleep? Science is here to help.
We have an armoury of evidence-based therapeutic and lifestyle tools to help us deal with sleep problems.
Sleep hygiene recommendations include the usual healthy diet and physical exercise tips. These include paying attention to ‘sleep hygiene’ including avoiding stimulants, keeping your bedroom dark and cool, and limiting artificial light sources after sundown.
Dr Jen Gunter recommends the following insomnia-specific CBT practices:
- Make a sleep schedule whereby you wake at the same time each day regardless of plans and have a set bedtime.
- Eliminate long daytime naps (this is hard but only necessary if you haven’t mastered the fine art of the strategic 20-minute power nap)
- Limit anxiety-provoking or stimulating activities before bed.
- Establish that bed is for sleep and sex.
In addition, Andrew Huberman a Stanford University neuroscientist who I’ve known since I was a doctorate student, recommends viewing sunrises and sunsets to regulate sleep-wake cycles.
“Among the many gifts that neuroscience research has brought in the last 10 years are the findings that viewing sunlight circa-dawn/sunrise and circa-sunset provides the strongest cue for aligning wake-sleep rhythms…
…viewing sunlight when it is low in the sky twice a day is the most powerful thing we can do for these bio-timing mechanisms that pervade all the cells, organs, and tissues of our body.”Professor Andrew Huberman
And finally, my oldest childhood friend is a psychiatrist and says she often counsels her patients that waking up, especially as you get older, is perfectly normal.
Lying there worrying you’re not getting your required unbroken eight hours (among other concerns) makes things worse. It’s easy to get caught in a vicious cycle of wakefulness and worrying, with night sweats and mood disorders giving ample time for minds to ruminate in the wee small hours.Dr Carol Dean, MB ChB FRANZCP
About Dr Sarah
I’m an Oxford University-educated neuroscientist, presenter of ABC Catalyst, director of The Neuroscience Academy, and author of The Women's Brain Book. The neuroscience of health, hormones and happiness.
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