Sleepy secrets (memory!) & coffee, circadian rhythms, wearables, nightwalking, insomnia (*and a signed book competition)

(Music - songs about coffee, sleep, and dreams; Poetry)

We humans have a peculiar relationship to one of our most-profound and well-being enhancing and renewing, biological, drives - namely, sleep. We need it, we want it, we love having had a good one, and we deny ourselves it. When your pet dog is tired, it just curls up in a comfortable spot, and a few seconds later, it’s gone. Your cat: ditto.

Whereas we humans will stay up – ‘just a for a little bit longer’ – because binge-watching, while knowing we must get up early for that unnecessary, early-morning, meeting (I’ll discuss recent research on meetings again), because coffee* will be your friend. We top and tail sleeping in a way no other species does – but sleep pressure builds, and sleep we must.

And not sleeping – going around sleep-deprived – is a disaster for body and brain. When you’re tired, you’re more likely to have a fatal traffic accident, for example: all those public service adverts telling you to coffee-nap (double espresso + forty winks) if you’re tired while driving have a really serious point. Driver fatigue is dangerous – whether you are behind the wheel of a car, a truck, a bus or a train – or trying to quickly steer out of the way of someone coming at you quickly because they’ve drifted off behind the wheel.

We now know lots about the effects of chronic sleep deprivation: it has malign effects on every organ system tested. Wound healing proceeds more slowly under chronic sleep deprivation; shrinkage of tissue in parts of the brain concerned with learning and memory can happen too. And sleep problems are very common – and disorders like insomnia and sleep apnoea are very personally distressing and come with strong health warnings.

Now, let’s look at some positive news about the benefits of sleep – there are some wonderful studies ongoing in sleep science – so here’s one recent study with important implications, for it shows that sleep quality over days and weeks predicts exam performance in college students.

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A marvelous study by Kana Okano and colleagues measured sleep quality, duration, and consistency in chemistry students in college. The key question was how much exam performance was affected by how well students slept – how regular their sleep, how good was the quality of their sleep, and the like. Having a vague feeling that sleep is good for you is one thing; knowing how, why and what duration is quite another. Okano and colleagues gave wearable activity trackers to 100 students enrolled in a chemistry class (88 completed the study). They found that ‘better quality, longer duration, and greater consistency of sleep correlated with better grades. However, there was no relation between sleep measures on the single night before a test and test performance; instead, sleep duration and quality for the month and the week before a test correlated with better grades’.

In other words, losing some sleep the night before because of pre-test nerves (or whatever) has little to no impact on exam performance – so long as you have been sleeping well in the weeks and months before the exam – you can, to a certain extent, ‘cognitively bank’ good sleep. Overall, good sleep accounted for about 25% of exam performance (obvy, you need to do your work too!).

Go to class, study, have good study habits based on the science of learning (and not the gibberish of learning styles). There are lots of reasons why sleep has such an impact, but one, rock-solid reason is that sleep enhances and stabilises the consolidation of memories, and sleep facilitates knowledge restructuring in the service of problem-solving (there’s a reason why we ‘sleep on it’: e.g., this; this; this; this; this). John Steinbeck, famously and insightfully, wrote that ‘It is a common experience that a problem difficult at night is resolved in the morning after the committee of sleep has worked on it.’ Okano and colleagues actually say ‘it may be more important to sleep well for the duration of the time when the topics tested were taught’.

Their data also point in an interesting and unexpected direction. There is a well-known gender difference in exam performance, with females often out-performing males in school and college systems across the world. Kano and colleagues might have stumbled upon at least one reason why: ‘we found that males required a longer and more regular daily sleep schedule in order to get good quality sleep. This female advantage in academic performance was eliminated once sleep patterns were statistically equated, suggesting that it may be especially important to encourage better sleep habits in male students (although such habits may be helpful for all students)’ (emphasis added). In other words, the difference in male-female exam performance at a population level might be ironed-out by ensuring better quality and quantity of sleep. So maybe cut-out all that early-morning training for sports, and do it at a time that fits better with the sleep-wake cycle? And cut-out late night shifts on the gaming console too…! An interventional study that remedies problems in sleep hygiene could test this idea out quite easily.

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One other thing: studies like this also demonstrate the usefulness of wearables for studying sleep ‘in the wild’. The measures you get are real world ones (or at least closer to real world ones). This is really important, because relying on self-reports of sleep patterns is notoriously unreliable – people’s memory of their sleep is confounded.

Caveat: the authors don’t overextend their findings, saying  that establishing ‘a causal relation between sleep and academic performance will require experimental manipulations in randomized controlled trials, but these will be challenging to conduct in the context of real education in which students care about their grades’. But knowing everything else we know about sleep and memory, the advice to practice good sleep hygiene because it offers spillover and indirect benefits for cognition, and for real-world exam performance, is extremely-well founded.

In summary: get regular, good quality, sleep: it’s one of the very best things you can do to promote and sustain health of brain and body. Furthermore, shun those fools who pretend they get by on a few hours sleep per night. There are lots of real-world examples, and they are generally not nice people. And don’t get into a car with them…

A final thought: as readers of this newsletter know, I love to walk, and to walk a lot. I have a notion – an untested hypothesis, for which I can offer no data, but which seems reasonable to me – that a walk at night-time in the hour or so before bed facilitates sleep.

Now why do I think this? For several reasons. Ambient lighting at night is very different to the morning, so the light-paced circadian rhythm that controls sleep is amplified – you’re getting a signal, via the eyes that it is, in fact, night-time (unlike our brightly-lit homes, with those bright 60 inch TeeVees!). Temperatures are generally lower at night outdoors, and we actually dump heat while sleeping at night (with core body temperature drifting down by about 1 degree C or so as we sleep, with body temperatures rising as we start to come close to waking up again) – so there is another environmental signal that it is time to sleep. The soundscape changes profoundly at night also (there is some evidence that circadian changes also have auditory contributions, and that noise causes dysregulation of circadian rhythms). There is also an adaptive value to sleeping at night – it’s much safer – the risk of falls, predation, and all the rest of it – are all reduced. Adding these together – and I think a night-walk might just be a useful adjunct to help falling asleep. (Anyone care to fund a randomised, controlled trial on this?!)

*and a book competition…

Thanks for reading to here! I want to give one lucky follower a chance to win a personally signed and dated copy of my book ‘In Praise of Walking’ to have for Christmas 😀 

Simply like and share this post: the winner will be announced here next Wednesday 25 Nov 👍 #wellbeing #walking #writing #reading #competition #aerobic  #brainhealth #braintraining

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Poetry

Try Thomas Kinsella’s great poem celebrating the urban, Nightwalker, where walking through Dublin at night, the poet writes that ‘the shadows are alive. They scuttle and flicker / Across the surface’.

Music - some sleepy stuff

*- a recent paean to coffee: Powfu - death bed (coffee for your head) (Official Video) ft. beabadoobee

And the original:

Roy Orbison - In Dreams (Black & White Night 30)

15 more songs about sleeping

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