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It's not just the amount of sleep that matters - timing is also key: Wisdom wednesdays · Hardiness with Dr Paul Taylor

• 0:05
  Speaker 1: Everybody, Welcome to another edition of Wisdom Wednesdays, and today
• 0:10
  Speaker 1: I want to talk about sleep. Now. When we talk
• 0:12
  Speaker 1: about sleep and the importance of sleep, almost always the
• 0:16
  Speaker 1: talk is about quantity. Did you get seven rs? Did
• 0:19
  Speaker 1: you get eight hours?
• 0:20
  Speaker 2: Are you making up for the sleep that you missed
• 0:22
  Speaker 2: during the week.
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  Speaker 1: And we tend to think of sleep as though it's
• 0:26
  Speaker 1: a kind of a bank account where the only thing
• 0:28
  Speaker 1: that matters is the final balance, and people talk about
• 0:31
  Speaker 1: sleep banking and sleep debt and all of these things.
• 0:35
  Speaker 1: But your body doesn't only count how many ours your sleep.
• 0:38
  Speaker 1: It also pays attention to when those hours occur and
• 0:42
  Speaker 1: whether it can predict the pattern from one day to
• 0:45
  Speaker 1: the next.
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  Speaker 2: So this is about sleep rhythms.
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  Speaker 1: And a major study published in the Journal of Epidemiology
• 0:52
  Speaker 1: and Community Health suggests that two people can achieve a
• 0:56
  Speaker 1: similar amount of sleep and still carry different cardiovascular risk
• 1:01
  Speaker 1: profiles and actually quite different because one sleeps at roughly
• 1:06
  Speaker 1: the same time each night, while the other is constantly
• 1:09
  Speaker 1: shifting between early nights, late nights, early mornings, and weekend sleeping,
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  Speaker 1: which is, let's face it, what quite a lot of
• 1:17
  Speaker 1: people do you now. This study involved a little bit
• 1:21
  Speaker 1: over seventy two thousand adults from the UK Bio Bank.
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  Speaker 1: So this is this huge, big database of people and
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  Speaker 1: they're studying lots of different things and it's producing so
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  Speaker 1: much cool research. But the adults in question here were
• 1:35
  Speaker 1: between forty and seventy nine years of age, and each
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  Speaker 1: person had a risk device for seven days, allowing the
• 1:43
  Speaker 1: researchers to estimate when they were asleep and when they
• 1:47
  Speaker 1: were awake. Right, and it's just about sleep and wake
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  Speaker 1: times that those risk devices aren't that great for stages,
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  Speaker 1: but they are good for estimating when you're asleep and
• 1:57
  Speaker 1: when you're awake. And from that information they calculated something
• 2:01
  Speaker 1: called the sleep regularity index or SRI, which measures how
• 2:07
  Speaker 1: consistently someone is asleep or awake at the same points
• 2:10
  Speaker 1: in time from one day to the next. Now this
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  Speaker 1: is worth explaining because it isn't simply a measure of
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  Speaker 1: whether you went to bed.
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  Speaker 2: At ten o'clock or midnight.
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  Speaker 1: It captures the overall stability of your sleep wake pattern,
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  Speaker 1: your sleep rhythms, if you like, including variations in what
• 2:27
  Speaker 1: time you got to sleep, waking time, also duration and
• 2:31
  Speaker 1: the interruptions across that sleep period. Now, the researchers then
• 2:35
  Speaker 1: followed these people for an average of just under eight years,
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  Speaker 1: and they used hospital and death records to identify heart attacks, strokes,
• 2:43
  Speaker 1: and heart failure, and they excluded people who'd already experienced
• 2:49
  Speaker 1: one of these events because they were at a greater
• 2:51
  Speaker 1: risk for it happening again. And they also removed events
• 2:54
  Speaker 1: that occurred during the first year of follow up in
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  Speaker 1: an attempt to reduce the possibility that some underlying undiagnosed
• 3:02
  Speaker 1: illness was already disrupting someone's sleep. So it's a pretty
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  Speaker 1: good study design. And during the follow up period there
• 3:10
  Speaker 1: were nearly five thousand major cardiovascular events eight hundred and
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  Speaker 1: eighty seven And when the researchers compared the groups, the
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  Speaker 1: most irregular sleepers had a whopping twenty six percent higher
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  Speaker 1: relative hazard of experiencing a major cardiovascular event than the
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  Speaker 1: most regular sleepers. People in the moderately irregular group had
• 3:36
  Speaker 1: approximately an eight percent higher hazard. So, again, this is
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  Speaker 1: an observational study, but you get strength of this study,
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  Speaker 1: or more confidence in the study if there's what we
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  Speaker 1: call a dose response, as in the people who had
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  Speaker 1: worse sleep for worse than people who were moderate.
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  Speaker 2: Right, And also when there's applausible.
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  Speaker 1: Biological mechanism that then strengthens our faith if you like,
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  Speaker 1: in this study, and there is a very good, plausible
• 4:02
  Speaker 1: biological mechanism.
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  Speaker 2: Now, what it doesn't mean.
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  Speaker 1: It doesn't mean that a regular sleep definitely caused twenty
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  Speaker 1: six percent more heart attacks, nor does it mean that
• 4:12
  Speaker 1: your personal chance of having a heart attack rises by
• 4:15
  Speaker 1: twenty six percentage points because you stayed up later on
• 4:18
  Speaker 1: a Saturday night. But what it does mean across this
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  Speaker 1: large population is that the rate of cardiovascar events during
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  Speaker 1: follow up was twenty six percent.
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  Speaker 2: Higher in the most irregular group.
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  Speaker 1: After the researchers adjusted for a substantial list of potential confounders,
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  Speaker 1: so this is pretty damn significant. They adjusted for factors
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  Speaker 1: including age, sex, ethnicity, socioeconomic status, physical activity, screen time, diet, coffee, alcohol, smoking,
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  Speaker 1: mental illness, medications, shiftwork, family history, and self reported sleep problems,
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  Speaker 1: and even after all of those adjustments, the association remained.
• 5:00
  Speaker 1: An interesting question that the researchers also explored was whether
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  Speaker 1: the irregular sleepers were just simply sleeping less and it
• 5:07
  Speaker 1: was time that was the issue. Right, Perhaps that sleep
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  Speaker 1: regularity was only acting as a proxy for inadequate duration.
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  Speaker 1: In other words, perhaps people with chaotic schedules were also
• 5:19
  Speaker 1: getting five or six hours sleep, and it was the
• 5:22
  Speaker 1: sleep deprivation rather than the timing that mattered. Now, to
• 5:25
  Speaker 1: investigate this, the research has divided people in to whether
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  Speaker 1: they met the sleep duration recommendations for their age group,
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  Speaker 1: and these were seven to nine hours for adults under
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  Speaker 1: sixty five and seven to eight rs for adults over
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  Speaker 1: sixty five. And among the moderately regular sleepers who achieved
• 5:44
  Speaker 1: those recommended ours, the excess cardyvaster association was no longer
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  Speaker 1: statistically clear right, so it did have an impact there.
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  Speaker 1: Hazard ratio was one point zero seven, so seven percent
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  Speaker 1: increased risk, but the confidence interval crossed one, meaning the
• 6:01
  Speaker 1: researchers could not rule out that there was no meaningful
• 6:05
  Speaker 1: difference from the regular sleepers group. However, amongst the most
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  Speaker 1: irregular sleepers who achieve the recommended duration, the hazard remain
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  Speaker 1: nineteen percent higher than in regular sleepers. So getting enough
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  Speaker 1: sleep appeared to reduce some of the problem, but it
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  Speaker 1: did not completely erase the association. It was still a
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  Speaker 1: pretty damn strong association. Nineteen percent higher risk of cardiovascular
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  Speaker 1: events is not insignificant. Now, this does not mean that
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  Speaker 1: sleep duration is suddenly unimportant. There's decades of evidence that
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  Speaker 1: tell us that chronically short sleep is associated with poorer
• 6:42
  Speaker 1: cardio metabolic health as well as increased risk of neurodegenerate diseases.
• 6:47
  Speaker 1: And this study is not designed to look at that evidence.
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  Speaker 1: But what it suggests is that duration is not the
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  Speaker 1: whole story. Sleep has several dimensions, how long you sleep,
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  Speaker 1: how well you sleep, and when you sleep on, how
• 7:01
  Speaker 1: consistent that pattern is and why might this regularity or the.
• 7:07
  Speaker 2: Rhythm be important.
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  Speaker 1: Well, you may have heard me talk about body having
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  Speaker 1: circadian clock. There's a central cicadian clock in the brain
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  Speaker 1: and your super chismatic nucleus, but it also contains clocks
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  Speaker 1: throughout the peripheral tissues, including your heart, your blood vessels,
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  Speaker 1: your liver, you panquish, your skeletal muscle, and these clocks
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  Speaker 1: help to organize predictable changes daily changes in blood pressure,
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  Speaker 1: heart rate, body rhythm, cortisole glucose regulation, immune function, and
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  Speaker 1: autonomic nervous system activity. Right now, the am is not
• 7:43
  Speaker 1: for these clocks to remain constant. Healthy physiology is rhythmic.
• 7:48
  Speaker 1: Cortisoles should not be identical at eight o'clock in the morning,
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  Speaker 1: eleven o'clock at night. Right, it peaks when you get
• 7:54
  Speaker 1: up in the morning, and it has got its lowest
• 7:56
  Speaker 1: point at night. Blood pressure and alertness change across the day.
• 8:00
  Speaker 1: The issue arises when your behavior, your light exposure, eating,
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  Speaker 1: in sleep continually occur at times your internal systems were
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  Speaker 1: not anticipating. So disrupting those biological rhythms really is.
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  Speaker 2: Bad juju for your health.
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  Speaker 1: And in a tightly controlled lab experiment, researchers invented participants behavioral
• 8:24
  Speaker 1: and environmental schedules by twelve rs, and even over a
• 8:29
  Speaker 1: relatively short period, circadan misalignment increase twenty four r blood
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  Speaker 1: pressure systolic by about three millimeters of mercury and raise
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  Speaker 1: several inflammatory markers.
• 8:41
  Speaker 2: Now, that experiment was far.
• 8:43
  Speaker 1: More extreme than staying up late occasionally, but it demonstrates
• 8:47
  Speaker 1: that circarean misalignment itself can alter your cardiovascar physiology. And
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  Speaker 1: the other thing as well is that most of your
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  Speaker 1: cells have got these internal clocks, so when you mess
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  Speaker 1: with your sleep rhythms, you actually mess.
• 9:00
  Speaker 2: With your biology.
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  Speaker 1: Now, there are other studies that have also linked a
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  Speaker 1: regular sleep with cardiovascular events, metabolic abnormalities, and markers of athleosclerosis.
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  Speaker 1: So this study that we mentioned isn't sitting on its own,
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  Speaker 1: but it's one of the largest studies to combine device
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  Speaker 1: measured sleep regularity with subsequent major cardiovascular events. And it
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  Speaker 1: just adds to the evidence that was already there. So
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  Speaker 1: what does this mean practically, right? And sleep regularity seems
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  Speaker 1: to be a pretty sensible target, right, and you don't
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  Speaker 1: need to have military precision around it. The objective is
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  Speaker 1: not to become anxious because your bedtime moved by ten minutes.
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  Speaker 1: Is to try to give your body a pattern that
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  Speaker 1: it could broadly predict, right. And I always say to people,
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  Speaker 1: try to go to bed within fifteen or twenty minutes
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  Speaker 1: of your normal time on most nights of the week.
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  Speaker 1: You know, we do have so showtimes when we're out
• 10:01
  Speaker 1: late and stuff like that, but when you're not doing that,
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  Speaker 1: it's about getting that rhythm both going to bed and
• 10:07
  Speaker 1: also wake time. Other research shows that you're waking time
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  Speaker 1: might be even more important. Right, So this is about
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  Speaker 1: picking a time that works for you with your responsibilities
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  Speaker 1: and you know, kids, all of those sorts of things,
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  Speaker 1: and try to keep it reasonably stable across the week,
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  Speaker 1: including weekends and don't shoot the messenger, people, that's just
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  Speaker 1: the message. Your bedtime can move in response to general sleepiness, right,
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  Speaker 1: But it's about trying to avoid those enormous swings where
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  Speaker 1: you go to bed at twelve thirty during the week
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  Speaker 1: and then two thirty in the morning on a weeknight,
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  Speaker 1: and then sleeping in late on the on the weekends.
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  Speaker 2: Now, the other really powerful lever that I have to
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  Speaker 2: mention here is light.
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  Speaker 1: Light entering your eyes is one of the main signals
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  Speaker 1: used by your brain to synchronize that internal clock in
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  Speaker 1: your super chismatic nucleus with the external world. And there's
• 11:00
  Speaker 1: lots of natural light studies that have shown that spending
• 11:04
  Speaker 1: more time exposed to outdoor light dark cycle can shift
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  Speaker 1: your cicadrean timing earlier than the pattern commonly seen in
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  Speaker 1: modern indoor environments.
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  Speaker 2: Right.
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  Speaker 1: So when we spend a lot of time indoors, we
• 11:17
  Speaker 1: tend to phase shift later, right, and naturally have later
• 11:21
  Speaker 1: go to bedtimes, which is a problem in itself in
• 11:24
  Speaker 1: terms of hormones as well. So a simple strategy here
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  Speaker 1: that I love to use is that the booke end
• 11:30
  Speaker 1: your day with natural light.
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  Speaker 2: Get outside as soon as you wake up.
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  Speaker 1: If you can rather than spending a first couple of
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  Speaker 1: hours in the morning in a dim house looking at
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  Speaker 1: a bright phone.
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  Speaker 2: You don't need to stir at the sun.
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  Speaker 1: It's just about getting out and being exposed to natural
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  Speaker 1: light and that helps to reset your cicicidian rhythm. And
• 11:54
  Speaker 1: then another key thing is to try to get another
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  Speaker 1: period of outdoor light in the afternoon, late afternoon and
• 12:02
  Speaker 1: particularly around sunsets. So it's these yellow we rays from
• 12:05
  Speaker 1: the sunrising and sunsetting that actually have a big impact on.
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  Speaker 2: Our circadian rhythms.
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  Speaker 1: Morning light generally shifts a delayed body clock earlier, and
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  Speaker 1: so getting that early like can be really effective if
• 12:19
  Speaker 1: you're one of these people who called yourself a night earl,
• 12:21
  Speaker 1: if you tend to go to bed really late, right,
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  Speaker 1: But like I said, the key thing is about regularity
• 12:29
  Speaker 1: and rhythm. So the message from this research is not
• 12:31
  Speaker 1: that seven or eight hours no longer matters. It's that
• 12:34
  Speaker 1: the body wants both adequate sleep and it wants a
• 12:37
  Speaker 1: predictable rhythm that it can recognize. So it's about aiming
• 12:41
  Speaker 1: for enough sleep and good quality.
• 12:43
  Speaker 2: But it's also about.
• 12:44
  Speaker 1: Paying attention to when you go to sleep and also
• 12:48
  Speaker 1: when you get up and then using little tweaks to
• 12:51
  Speaker 1: make sure that you are in a natural rhythm, because
• 12:54
  Speaker 1: our bodies and our brains are all about these circarean
• 12:58
  Speaker 1: and ultradean and set the other rhythms.
• 13:01
  Speaker 2: So that's it for this week, folks, catch you next time.