I need to rant before I will borrow one hour of my life to some technocrats tomorrow – that will give it back to me in October. So the subtitle is:
I hate Daylight Savings Time!
Daylight Savings Time was inspired by a whimsical essay by Benjamin Franklin (probably not the first time that politics fell for something like the Sokal hoax?). The official goal was energy savings – and results are ambiguous. Frankly, I don’t care about that anyway. I believe that the losses in human productivity caused by misguided attempts to tinker with our biological clocks would outweigh those spurious gains.
I have read three books on sleep research and chronobiology recently to be entitled to write a more scientifically sounding post:
- Internal Time: Chronotypes, Social Jet Lag, and Why You’re So Tired by Till Roenneberg
- Dreamland: Adventures in the Strange Science of Sleep by David K. Randall
- The Twenty-four Hour Mind: The Role of Sleep and Dreaming in Our Emotional Lives by Rosalind Cartwright
Randall is a journalist who got interested in sleep research because he hurt himself while sleepwalking. Researching what science has to say about sleep he was then surprised to find out how few we know. Even the simplest assumptions are not sacred – sleep is not necessarily intended to be “consumed” as 8 hours at a time: Our ancestors (across cultures) wrote about the first sleep and the second sleep – two blocks of sleep interrupted by a longer break. Today such people might ask for medication to cure their insomnia.
Randall’s book gives an easy-to-digest summary of some results of sleep research and chronobiology – that seem to be distinct disciplines thanks to compartmentalization in science.
Sleep researcher Cartwright covers the nature of sleep as such. She tries to clarify why we need to “waste” one third of our lifetimes in this strange state of mind. Biologist Roenneberg explains what triggers sleep and how our internal clocks are synchronized with external cues. I recommend these two books by scientist pioneers in their fields. I was also most impressed by Cartwright’s CV who received her PhD in 1949 and published this book in 2010.
It is creepy and fascinating what people can do when sleepwalking, such as murdering their beloved ones without recollecting anything later. Both Randall and Cartwright cover exceptional cases that caused some stir in the media – summarized also in this publicly available scientific paper by Cartwright on sleepwalking violence (Link now broken) or this historical account.
However, not having any experience with disturbing actions by sleepers I was more interested in Cartwright’s central thesis of the mind being active 24 hours a day: Different phases of sleep allow for processing what we have encountered during the day and committing it to memory so to speak and to merge it with already existing emotional memories – to complement our very self with new input without compromising its integrity (My words – I know it sounds a bit like what the Borg say when assimilating other cultures.)
It is especially emotionally troubling “content” that requires processing – and in particular if the troubling nature was not obvious. This seems plausible to me: Isn’t it often an incidental remark dropped by somebody else that remains unresolved and bothers us longer than we consciously are aware of it? And that sleeping over it make the uneasiness go away?
Cartwright’s own research on patients depressed because of life events (divorces in that case) give prove of the healing power of REM sleep, depending on the capabilities of the patients’ “processing systems”: The change in patients’ moods after sleeping and during the day turned out to be an indicator of when and if patients would eventually recover from depression.
But I don’t care so much about the details here. As Nassim Taleb laid out in Antifragile: Don’t care about the scientific details of biological processes if you know from experience that they work (applied to fitness and health). Grandma knew it that sleep was important.
Having accepted that sleep needs to be good for something and science will eventually find out how that works in detail the really important question for us, practitioners of sleep, is: When and how much? And that’s why I found Roenneberg’s book most useful.
In a nutshell I have learned:
We really sleep 8 hours on average. It is not at all a shame not to comply with this ideal of Very Successful People who claim to or really need only 5 hours.
Midsleep is used to tell owls from larks – this is the midpoint of sleep in terms of local time. Midsleep indicates that we are not a world of early risers: The distribution peaks between 4 and 5AM! So actually most of us rise shortly after our biological midnights.
Roenneberg speculates about some professions being self-selective for early risers and short sleepers – especially decision makers. So there might be some truth to that magazine articles about A Day in the Life of Somebody Very Important who gets up at 4:00AM to meditate in the Zen garden, then plays with the kids, then heads to the airport – quickly buying and selling some companies over the phone,…, and finally meeting other important beings for wine-tasting and networking in the evening.
If human beings are left to themselves in a time-free bunker – even shielded from vibrations caused by vehicles or the earth’s magnetic field – most of them are guided by a free-running clock with a 25 hours period. However, experiments showed that some of the “days” might even last for up to 50 hours, and subjects don’t notice – they also eat only half of the meals. A minority of larkish people is equipped with an internal clock with a period of less than 24 hours.
There was no evolutionary need to come up with a precise free-running clock because the internal clock gets synchronized daily to the rotation of the earth via external zeitgebers. (German for “time givers” / “signals”. I was delighted to learn that Germans pioneered chronobiology so not only eigenvalue and kindergarten entered the English language).
The most interesting part for the physicist in me was to learn how this so-called entrainment works. It is about phase-locking two oscillating systems, a process well-known in physics (Here is a paper for the mathematically inclined, and here is an overview by Roenneberg that is a bit more detailed than the related chapter in the book).
These models naturally explain why an internal 25 hours clock has to result in owlish behavior:
The zeitgeber is light – sunlight or other, the wavelength does not seem to matter much but the intensity and the point of time does: Roenneberg uses the analogy of the proverbial child on a swing as the free-running oscillator – which is pushed by a person, the zeitgeber, periodically. Consider the pusher acting on the swing at different times – it will either accelerate or decelerate the swing, depending on the relation of phases so to speak.
The natural zeitgeber pushes continuously and its effect and strength determines on the time of the push:
- When it pushes before the internal clock reaches its internal midday it tells the internal clock to hurry up.
- When it pushed at the “internal afternoon” it tells the internal clock to slow down.
If the internal midday would coincide with the sun’s midday the effects would cancel – in the first half of the day the period is compressed but in the second half expanded again.
If the internal midday occurs well after the sun’s midday then the expansion effect is not as effective as the compression effect: Owls make more use of the compression part of the cycle than of the expansion part The sun has already set when it would need to expand the day again. These sleepers “have to” get up late sp that they their internal midday is shifted to the external clock’s afternoon.
For larks it works exactly in the opposite way: They are early risers to fully benefit from the expansion while part of the potential compression effect of the zeitgeber remains hidden in the period before sunrise.
You cannot re-engineer your genetic make-up (yet) – the clock itself is built up from something like a little production line of proteins – a cycle that is complete over and over. Lifestyle has of course an impact as:
- Artifical light during the day is a zeitgeber too weak during the day but too strong in the evening. Farmers tend to be earlier than office workers on average.
- Cities are polluted with light – so people in rural areas are earlier than city dwellers.
But we still trace the sun: From an impressive database of sleeping routines of Germans all over the country Roenneberg concluded that:
Inhabitants of Eastern Germany wake up earlier by some minutes – and alleged cultural remainders of “former East Germany’s work ethics” are easily debunked by noting that also former West German cities at equally Eastern latitudes fit the pattern.
Now guess: Until when do waking hours exactly change with the sun rising at a different time every day? It is exactly until the dreaded last Sunday in March. Exactly until October when we get our precious hour back, our waking hours are erratic and uncorrelated with sunrise. It is interesting that these points of time are not even symmetrical to the equinox so it is difficult to come up with any other explanation than DST severely messes up the internal clock.
Roenneberg generally turns these “sociological” explanations on their heads, such as the so-called disco hypothesis that states that teenager simply should party less and go to bed earlier. But teenagers become owls and turn earlier again in their twenties. It might be explained by an evolutionary advantage in stone-age cultures where young men were on a hunt all the night and not the whole tribe slept at the same time. What if teenager party because they cannot sleep and not the other way round?
About 60% of grown-up people in Germany work schedule against their inner clocks today – so why impose the falsely glorified Early Bird’s lifestyle on them, such as school starting at 8:00 AM or earlier? I think Roenneberg is right in assuming the self-selecting effect of decision makers, teachers and doctors. Politicians are always ready to utter the stereotypical Children are our future! (when asked to give a speech on opening the renovated school) but they see insurmountable barriers in changing the timetables of local buses that absolutely have to transport both school children and workers.
I am absolutely baffled by the ignorance of scientifically (or better empirically) proven facts – for the sake of purporting cultural myths and questionable ideals.
As I know too well you can turn yourself into a fake short sleeper and fake lark with sheer willpower and misguided self-discipline that might be better invested elsewhere: I had quite a track record as the person who got e-mails like Do you ever sleep? as responses to e-mails I sent at 23:55 and then again at 4:05. This does not at all mean that you can ever sync your internal clock to that pattern and re-train as a lark. As Roenneberg explains: People need an alarm clock for decades of their careers and never “get used” to the larkish schedule.
My theory is that decision makers designing schedules for corporate employees or students are well aware of the pain of getting up in the morning as some of them have to be owls, too. I think it is the same social dynamics that is at play when the finally tenured professor forces overworked graduate students to put in more hours and asks why they don’t work on weekends or when heads of departments in hospitals expect young doctors to work the same insane schedules they had once, too.
If you have inflicted a grueling routine upon yourself for some years it is probably understandable that you can’t help but feeling – and uttering They should suffer, too! But it maybe should not become the assumption underlying political decisions.
Anyway: Happy DST morning!
More details in the internal clock by Roenneberg:
Life Between Clocks: Daily Temporal Patterns of Human Chronotypes by Roenneberg et al.