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REM sleep as Therapy · Hardiness with Dr Paul Taylor

• 0:05
  Speaker 1: Hey everyone, welcome to another edition of Wisdom Wednesdays. Today
• 0:10
  Speaker 1: we're going to talk about sleep. Now we all know
• 0:12
  Speaker 1: that sleep matters, but we tend to think about it
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  Speaker 1: in pretty crude terms. Did I get seven hours? Did
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  Speaker 1: I get eight hours? Did I sleep well? Interesting though,
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  Speaker 1: the research is suggesting that it's what happens within those.
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  Speaker 2: Hours that matters enormously.
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  Speaker 1: And I want to talk today about a particular stage
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  Speaker 1: of sleep that keeps cropping up in studies of brain health,
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  Speaker 1: emotional regulation, dementia, cardiovascular disease, and even mortality. And that
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  Speaker 1: stage is not deep sleep. It's REM sleep or rapid
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  Speaker 1: eye movement. So REM is the strange part of sleep
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  Speaker 1: where your brain becomes remarkably active. Your eyes will flick
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  Speaker 1: rapidly beneath your eyelids. Vivid dreaming is coming for some people.
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  Speaker 1: And most of your skeletal muscles are temporarily paralyzed so
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  Speaker 1: that you don't physically act out your dreams. Now, for years,
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  Speaker 1: REM was seen largely as the dreaming stage of sleep,
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  Speaker 1: and Freud did a lot of analysis on it. But
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  Speaker 1: we now know that it appears to be involved in
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  Speaker 1: memory consolidation, emotional processing, and possibly a range of processes
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  Speaker 1: that influence long-term brain and cardiovascular health. Now, the interesting
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  Speaker 1: thing about REM is that it isn't evenly distributed across
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  Speaker 1: the night. You probably know that we cycle through the
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  Speaker 1: different stages of sleep roughly every 90 minutes, but the
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  Speaker 1: architecture changes as the night progresses. Earlier in the night,
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  Speaker 1: we tend to get proportionally more deep, slow-wave sleep, and
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  Speaker 1: that's important for a lot of physical repair. But as
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  Speaker 1: morning approaches, the REM periods become progressively longer. Now, that
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  Speaker 1: means cutting your sleep short doesn't simply remove an equal
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  Speaker 1: chunk of sleep.
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  Speaker 2: Of every sleep stage.
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  Speaker 1: If your body needs eight hours and you regularly give
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  Speaker 1: it six, you're disproportionately sacrificing the REM-rich final part of
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  Speaker 1: the night. And that may turn out to be much
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  Speaker 1: more consequential than.
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  Speaker 2: Most people actually realize.
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  Speaker 1: So a fascinating study was published in PLOS Medicine in 2026.
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  Speaker 1: It brought this into really sharp focus. The researchers analyzed
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  Speaker 1: sleep in about 96,000 participants from the UK Biobank database.
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  Speaker 1: And these people had sleep stages had been estimated using
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  Speaker 1: wrist accelerometers. And then they followed them for a medium
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  Speaker 1: of almost nine years. And they examined more than 1,000
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  Speaker 1: subsequent health outcomes in these people. Now, the associations with
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  Speaker 1: REM sleep were pretty bloody extraordinary, I've got to say.
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  Speaker 2: And additional.
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  Speaker 1: 47.6 minutes of estimated REM sleep was associated with a
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  Speaker 1: whopping 46% lower risk of dementia, 26% lower risk of
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  Speaker 1: heart failure, 17% lower risk of atrial fibrillation and 13%
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  Speaker 1: lower risk of ischemic heart disease. Overall, REM sleep was
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  Speaker 1: associated with the subsequent risk of 83 different diseases, and
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  Speaker 1: that is bonkers. Now, those numbers do need to be
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  Speaker 1: interpreted properly. It was an observational study, and we all
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  Speaker 1: know the limits of observation studies. And REM sleep was
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  Speaker 1: estimated from devices that were on the wrist rather than
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  Speaker 1: measured directly from brain activity in a sleep lab. And
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  Speaker 1: that therefore cannot tell us definitively that adding about 48
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  Speaker 1: minutes of REM sleep will cut your dementia risk in.
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  Speaker 2: Almost in half.
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  Speaker 1: Healthier people may simply produce more REM sleep. Early disease
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  Speaker 1: processes may reduce REM sleep or REM itself may contribute
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  Speaker 1: to the protection.
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  Speaker 2: We don't really know.
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  Speaker 1: Biology is rarely considered enough to give us a very
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  Speaker 1: neat cause and effect when we observe.
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  Speaker 2: Things, right?
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  Speaker 1: However, it's not the only data set pointing in this
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  Speaker 1: direction and that is where the strength of our convictions
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  Speaker 1: actually increase. So a 2020 study published in JAMA Neurology
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  Speaker 1: looked at REM sleep measured during formal overnight sleep studies
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  Speaker 1: in the lab. One cohort of 2,675 older men followed
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  Speaker 1: for around 12 years. Every 5% each point reduction in
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  Speaker 1: REM sleep was associated with about a 13% greater risk
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  Speaker 1: of death. And a second cohort of roughly 1,400 adults
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  Speaker 1: followed for more than two decades showed a similar relationship.
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  Speaker 1: with around a 17% increase in mortality risk for every 5%
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  Speaker 1: reduction in REM sleep. Now, again, this doesn't prove that
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  Speaker 1: REM prevents early death, but when different studies using different
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  Speaker 1: populations and methods start producing similar signals, it really becomes
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  Speaker 1: worth paying attention to. Now, the dementia research is equally interesting.
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  Speaker 1: In the famous Framingham Health study, Researchers followed 321 people
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  Speaker 1: who'd undergone overnight sleep studies and they followed it up
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  Speaker 1: for 19 years. People who subsequently developed dementia had tended
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  Speaker 1: to spend a smaller proportion of their sleep in REM
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  Speaker 1: and each percentage point reduction in REM was associated with
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  Speaker 1: roughly a 9% increase in dementia hazard in their initial model.
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  Speaker 2: And then in.
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  Speaker 1: 2025, another group approached the question differently. they measured how
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  Speaker 1: long it took 128 participants to enter their first REM
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  Speaker 1: period and compared this with Alzheimer's biomarkers. So people with
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  Speaker 1: particularly delayed REM sleep showed greater amyloid burden, higher phosphorylated tau,
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  Speaker 1: and lower BDNF. You may have heard me talk about BDNF.
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  Speaker 1: That's a protein involved in neuronal health and neuronal plasticity. Now,
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  Speaker 1: once again... we cannot turn association into cause. Early Alzheimer's
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  Speaker 1: pathology could disturb REM sleep, so it could work in
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  Speaker 1: the other direction. Poor REM could theoretically contribute to the pathology.
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  Speaker 1: Both processes could also reinforce each other. And at the moment,
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  Speaker 1: we simply don't know definitively. But what we do know
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  Speaker 1: is that REM appears to be doing something extremely interesting
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  Speaker 1: inside the brain. Now, one of those things is memory consolidation.
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  Speaker 1: During REM sleep, Prominent theta rhythms occur in areas in
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  Speaker 1: the brain involved in learning and memory. And in a
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  Speaker 1: particularly cool 2016 experiment published in the journal Science, researchers
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  Speaker 1: selectively interfered with REM-related theta activity in mice, and the
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  Speaker 1: animals subsequently performed worse.
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  Speaker 2: On memory tasks.
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  Speaker 1: And that provided causal evidence that at least some of
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  Speaker 1: the neural activity occurring during REM sleep contributes to memory consolidation.
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  Speaker 1: But for me, the most fascinating REM research concerns emotion.
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  Speaker 1: I wrote about this in my book, Death by Comfort
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  Speaker 1: and the Hardiness Effect. And it was based on work
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  Speaker 1: from Ricky Wassing and colleagues at the Netherlands Institute for Neuroscience.
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  Speaker 1: Their 2019 study, published in the journal Current Biology... investigated
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  Speaker 1: what happens to emotional experiences when we sleep. So what
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  Speaker 1: the researchers did was they induced a self-conscious emotional response
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  Speaker 1: in volunteers and measured their brain responses using functional MRI.
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  Speaker 1: The participants then slept while their sleep was measured using EEG.
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  Speaker 1: And the researchers were particularly interested in the amygdala, one
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  Speaker 1: of the brain regions involved in processing emotionally salient and
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  Speaker 1: threatening information. What they found was fascinating. Amygdala reactivity decreased
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  Speaker 1: overnight in proportion to the amount of consolidated REM sleep
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  Speaker 1: that people obtained. In other words, good quality REM seemed
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  Speaker 1: to help the emotional brain adapt and process what had happened.
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  Speaker 1: But when REM was restless and repeatedly interruption, that adaptation
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  Speaker 1: was impaired. Now, this fits beautifully with what animal research
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  Speaker 1: has shown about an area in the brain called the
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  Speaker 1: locus coeruleus. This is a tiny brain stem structure that's
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  Speaker 1: the brain's major source of noradrenaline, the sister chemical of adrenaline.
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  Speaker 1: If you're American, it's norepinephrine. Now, normally, the locus coeruleus
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  Speaker 1: becomes remarkably quiet during REM sleep. Animal experiments have shown
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  Speaker 1: that abnormal activity in this system during periods when it
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  Speaker 1: should be silent can interfere with sleep-related brain plasticity and
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  Speaker 1: memory processes. So basically, if you think about it, if
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  Speaker 1: that area is silent, the bit that produces no adrenaline
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  Speaker 1: during REM sleep, it means that you're remembering those days'
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  Speaker 1: events differently but in the absence of stress, right? And
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  Speaker 1: that gives us a fascinating hypothesis about what REM might
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  Speaker 1: be doing. So during the day, if something stressful happens,
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  Speaker 1: that memory becomes associated with a physiological emotional response. Your
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  Speaker 1: heart races, your stress hormones rise, and the amygdala fires up.
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  Speaker 1: During REM sleep, the brain appears to replay and reorganize
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  Speaker 1: emotionally important memories in an environment where no adrenaline is dramatic.
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  Speaker 2: Reduced.
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  Speaker 1: So in simple terms, the brain may be revisiting the
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  Speaker 1: memory without reproducing the full stress response. You remember what happened,
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  Speaker 1: but some of the emotional sting gets stripped away. Now,
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  Speaker 1: Matthew Walker and Els van der Helm have described a
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  Speaker 1: related idea as sleep to remember and sleep to forget.
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  Speaker 1: You retain the information, but gradually lose some of the physiological.
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  Speaker 2: Charge attached to it.
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  Speaker 1: And that's why I sometimes describe REM sleep as nightly
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  Speaker 1: therapy for the brain. Now, Wassing's team produced another fascinating
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  Speaker 1: experiment around the same time that makes the story even stronger.
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  Speaker 1: They induced the emotion of shame, which is a very
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  Speaker 1: powerful emotion, in 64 participants by replaying recordings of them
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  Speaker 1: singing karaoke, including some apparently spectacularly bad performances. Now, the
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  Speaker 1: participants were exposed repeatedly to across three days, allowing the
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  Speaker 1: researchers to compare how emotional distress changed after periods of
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  Speaker 1: wakefulness and sleep.
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  Speaker 2: It's a cracking study.
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  Speaker 1: Now, for normal sleepers, sleeping after the experiment reduced part
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  Speaker 1: of the physical distress associated with the shame response. And
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  Speaker 1: people with insomnia, however... something almost opposite happened. Their physical
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  Speaker 1: distress became worse overnight. The researchers concluded that poor sleep
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  Speaker 1: can actually become maladaptive rather than merely failing to produce
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  Speaker 1: the normal emotional benefits of sleep. So it actually can
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  Speaker 1: make it worse. And this helps explain something we see
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  Speaker 1: consistently in the relationship between sleep and anxiety. We often
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  Speaker 1: think I'm anxious, therefore I can't sleep. And that certainly
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  Speaker 1: is true. Anxiety can make sleep bloody difficult. But the
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  Speaker 1: arrow also travels in the opposite direction. If your sleep
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  Speaker 1: is repeatedly fragmented, particularly your REM sleep, your brain may
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  Speaker 1: become less effective at recalibrating emotional experiences from the previous day.
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  Speaker 1: So you wake up carrying more of yesterday with you,
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  Speaker 1: you become more emotionally reactive, you sleep worse the following night,
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  Speaker 1: and a fairly nasty feedback loop can develop. Now, interestingly,
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  Speaker 1: a commentary published alongside the Washing research noted that REM
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  Speaker 1: appears to play an important role in processing and consolidating
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  Speaker 1: emotional memory while restless REM interferes with this process. So
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  Speaker 1: there's another REM phenomenon That's worth knowing about because people
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  Speaker 1: sometimes confuse it with simply getting too little REM. During
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  Speaker 1: normal REM sleep, your muscles, as I said earlier, are
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  Speaker 1: largely paralyzed to stop you physically acting out your dreams.
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  Speaker 1: So in REM sleep behavior disorder, or known as RBD,
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  Speaker 1: this paralysis feels and people may kick, punch, shout, or
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  Speaker 1: physically enact what they're dreaming. Now, this is very different
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  Speaker 1: from your Garmin telling you you only had 47 minutes
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  Speaker 1: of REM last night. RBD is recognized as a neurological condition,
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  Speaker 1: and it's important because it can precede disorders such as
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  Speaker 1: Parkinson's disease and dementia with Lewy bodies by many years. Now,
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  Speaker 1: in a large multi-study center involving 1,280 people with confirmed
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  Speaker 1: idiopathic RBD, the rate of progression to a neurodegenerative disorder
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  Speaker 1: was around 6.3% per year. So what do we do
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  Speaker 1: with all of this? The first thing is, it's not
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  Speaker 1: about hacking your REM sleep. Your body has spent a few,
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  Speaker 1: or our bodies have spent a few million years working
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  Speaker 1: out how to organize sleep and probably doesn't need an
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  Speaker 1: influencer with a supplement stack to improve it. The most
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  Speaker 1: effective strategy is to protect normal sleep architecture. Now, the
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  Speaker 1: obvious starting point is giving yourself enough time in bed,
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  Speaker 1: Because REM becomes increasingly prominent towards morning, regularly cutting that
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  Speaker 1: last hour or two from your sleep is particularly likely
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  Speaker 1: to reduce REM. If you biologically need eight hours and
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  Speaker 1: consistently allow yourself only six and a half, there's no
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  Speaker 1: amount of magnesium, sleep spray or expensive mattress that's going
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  Speaker 1: to fully compensate for.
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  Speaker 2: That missing time. Now, alcohol is a particularly big one.
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  Speaker 1: Alcohol can certainly make you sleepy and help you fall asleep,
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  Speaker 1: but sedation is not the same thing as healthy sleep.
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  Speaker 1: And a 2025 systematic review and meta-analysis found that alcohol
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  Speaker 1: alters sleep architecture and can delay and disrupt REM sleep.
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  Speaker 1: That's why the traditional nightcap is something of a biological
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  Speaker 1: con trick. It can help you fall asleep, while simultaneously
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  Speaker 1: degrading the quality of the sleep that you get, especially REM.
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  Speaker 1: And in the Hardiness Effect book that I wrote, I
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  Speaker 1: put it more simply. If REM is part of your
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  Speaker 1: brain's overnight therapy, then more alcohol effectively means less therapy. Now,
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  Speaker 1: the other big thing worth taking seriously is clearly sleep apnea.
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  Speaker 1: Repeated breathing interruptions fragment sleep throughout the night, and they
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  Speaker 1: completely disturb normal sleep architecture. So if you snore heavily,
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  Speaker 1: your partner notices that you stop breathing during a sleep,
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  Speaker 1: you wake up gasping, or you remain exhausted despite spending
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  Speaker 1: enough time in bed, it's time to get it properly assessed, right?
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  Speaker 1: There's little point in obsessing over your REM score while
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  Speaker 1: ignoring a treatable sleep disorder. Now, temperature seems to matter
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  Speaker 1: a hell of a lot, right? Even more than light,
• 15:49
  Speaker 1: it turns out. Sleep is facilitated by a fall in
• 15:53
  Speaker 1: core body temperature and excessive heat can induce wakefulness and
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  Speaker 1: reduce both deep and REM sleep. So the exact perfect
• 16:02
  Speaker 1: bedroom temperature varies between people, but it should be cool
• 16:07
  Speaker 1: and it also should be dark and quiet. And that
• 16:10
  Speaker 1: is a remarkably effective combination. Really, the ideal temperature seems
• 16:15
  Speaker 1: to be something between 16 and 19 degrees centigrade.
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  Speaker 2: For most people. Now, the other thing we need to
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  Speaker 2: talk about is medications.
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  Speaker 1: Some antidepressants and other drugs suppress or alter REM, although
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  Speaker 1: they affect very considerably by medication, by dose and by individuals.
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  Speaker 1: And the sensible response is not about stopping your medication
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  Speaker 1: because your wearable says you got low REM score. If
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  Speaker 1: your sleep has changed substantially after starting medication, you should
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  Speaker 1: probably go back to the doctor and have a discussion
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  Speaker 1: about it.
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  Speaker 2: Now, this brings us to wearables.
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  Speaker 1: I am a fan of wearable technology, and I think
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  Speaker 1: sleep tracking can be useful in parts, but you need
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  Speaker 1: to understand what the devices are actually measuring. In a
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  Speaker 1: sleep lab, stages of sleep are identified using polysomography, which
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  Speaker 1: measures electrical brain activity, eye movements, muscle activity, and a
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  Speaker 1: range of other physiological signals. Now, your Apple Watch, your Garmin,
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  Speaker 1: your Wootband, your Oura Ring, they can't directly see your
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  Speaker 1: brain activity.
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  Speaker 2: What they do is they combine signals such as movement of.
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  Speaker 1: Whatever hand that you're wearing that on, also your heart
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  Speaker 1: rate and heart rate variability, and then use algorithms to
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  Speaker 1: estimate what sleep stage that you're probably in. Now, there's
• 17:34
  Speaker 1: a 2025 independent lab study compared six commercial trackers with polysomography. Now,
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  Speaker 1: all of them were reasonably good at determining whether somebody
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  Speaker 1: was asleep, but sleep stage agreement wasn't that great. REM
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  Speaker 1: classification in the study was about 69% accurate for the
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  Speaker 1: Apple Watch Series 8, 62% accurate for Whoop 4.0 and 33%
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  Speaker 1: for the Garmin VivoSmart 4. Now, we shouldn't take those
• 18:06
  Speaker 1: numbers as gospel for those devices because with each iteration,
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  Speaker 1: the devices change and their algorithms change, right?
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  Speaker 2: So they may get better over time.
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  Speaker 1: Now, the Oura ring wasn't included in that particular comparison,
• 18:20
  Speaker 1: but there was a separate validation study of the Generation
• 18:23
  Speaker 1: 3 ring, and it compared it with multiple nights of
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  Speaker 1: polysomography in 96 adults. And that reported relatively good REM
• 18:32
  Speaker 1: stage classification. Now, because it was a different study using
• 18:36
  Speaker 1: different participants and methods, you can't really compare it directly
• 18:40
  Speaker 1: to the Apple Garmin and WHOOP and declare a winner.
• 18:43
  Speaker 1: But the sensible thing for these devices is to look
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  Speaker 1: at them as trends rather than precisely nightly numbers. And
• 18:52
  Speaker 1: we expect that if they're incorrect, they're consistently incorrect. So
• 18:56
  Speaker 1: it's looking at the trend over time. So if your
• 18:59
  Speaker 1: wearable normally estimates 90 minutes of REM and suddenly that
• 19:02
  Speaker 1: falls to 40 minutes for two weeks at the same
• 19:05
  Speaker 1: time that your sleep duration drops or your alcohol intake increases,
• 19:10
  Speaker 1: that's useful information. But if it says you had 46
• 19:13
  Speaker 1: minutes on Monday and 72 minutes on Tuesday, I wouldn't
• 19:17
  Speaker 1: lose a minute of sleep worrying about the difference.
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  Speaker 2: Now, ironically.
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  Speaker 1: Becoming anxious because your sleep tracker says you didn't get
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  Speaker 1: enough REM is a particularly stupid way of using a
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  Speaker 1: device that's supposed to improve your health, but it helps
• 19:30
  Speaker 1: with a lot of people. So if you look at
• 19:33
  Speaker 1: your watch and you get stressed about it, you should
• 19:35
  Speaker 1: probably not wear your watch or certainly not look at it.
• 19:38
  Speaker 1: So the bigger message is that REM sleep appears to
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  Speaker 1: be much more than this strange part of the night
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  Speaker 1: where we dream. Higher REM is consistently associated with better
• 19:50
  Speaker 1: outcomes across a surprisingly wide range of diseases and lower
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  Speaker 1: REM has been associated with increased mortality and dementia. REM-related
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  Speaker 1: brain activity appears to contribute to memory consolidation, and consolidated
• 20:06
  Speaker 1: REM seems to allow the emotional brain to recalibrate experiences
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  Speaker 1: from the previous day. So whether REM itself is directly protective,
• 20:16
  Speaker 1: whether it's a primarily a marker of a healthy brain
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  Speaker 1: or whether both things are true, that remains to be
• 20:24
  Speaker 1: firmly established.
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  Speaker 2: But I think if you've listened to this.
• 20:27
  Speaker 1: You probably draw the same practical conclusion as me. And
• 20:31
  Speaker 1: that is to protect your sleep, particularly the final hours
• 20:35
  Speaker 1: of the night. Be sensible with your alcohol consumption. Maybe one,
• 20:40
  Speaker 1: but if you're having more than one, it's definitely going
• 20:43
  Speaker 1: to affect with your REM. Deal with sleep apnea rather
• 20:46
  Speaker 1: than ignoring it if you think that you have it.
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  Speaker 1: keep your bedroom cool and dark, get your goddamn phone
• 20:52
  Speaker 1: out of your room and use your wearable as a
• 20:56
  Speaker 1: trend monitoring tool rather than treating every nightly REM estimator
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  Speaker 1: as gospel. But what is pretty clear is that last
• 21:04
  Speaker 1: hour of sleep that you sacrifice for watching Netflix, doing
• 21:08
  Speaker 1: emails or mindless scrolling on social media is probably doing
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  Speaker 1: you considerably more.
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  Speaker 2: Damage than you think. That's it for this week, folks.
• 21:17
  Speaker 2: Catch you next time.