Sleep turns out to be far more important to our health than we knew.
When I was a young lad dreaming of becoming a great scientist, I supposed all the middle-sized science was already done. New, original science would be about galaxies or subatomic particles.
So it was a great shock to me when studing psychology in the 1980s to learn there were no tenable theories about why we sleep. Theories, yes. But none tenable in the face of the evidence. Ridiculous! We spend a third of our lives asleep. A third of our lives unconscious and defenceless. Research – much of it mid-20th century and prompted by reports of torture techniques – had shown we can’t sustain sanity without dreaming. How could we not know why?
A startling article (Van Dongen et al. 2003, Sleep, Vol. 26, N°2, p.117ff) reported alarming cognitive damage from repeatedly getting a little less than a full night’s sleep. I stopped setting my alarm clock. The cognitive damage is clearly temporary. I wrote to Van Dongen in 2008 to learn what was known about recovery. Nothing. His team planned more research. But the absence of a general theory left them guessing what to study.
A decade later and the results are in. In the last twenty years we learned more about sleep than in the previous two millennia. Matthew Walker’s book Why We Sleep summarises it. You should read it. Until you can get hold of it, some key findings:
Sleep is more valuable to our health than even proper diet or exercise, and the costs of getting it wrong at least as severe. Poor sleep facilitates cancer, cardiovascular disease and dementia.
You can’t catch up. While your body will scramble to mitigate the effects of poor sleep, the benefits of the sleep you missed are gone. Just gone.
Your sleeping clock – whether you are an early or late riser – is fixed, not under your control. If you fall asleep too late you miss your early-sleep NREM dreaming; if you wake too early you won’t finish your late-sleep REM dreaming. They have different functions, and both are vital to your mental health.
Human sleep is naturally biphasic: a long sleep at night and a 1-hour nap in the early afternoon. That drowsiness after lunch is not to be resisted. Take a siesta.
It is hard to exaggerate the benefits of the siesta. A Greek study examined just one measure. In a field in which statistically significant differences of 5% are considered large, across the population those who took no siesta were found 37% more likely to be diagnosed with cancer. For working men, that figure rose to 60%.
Drowsy driving is even more dangerous than driving drunk. Drowsiness results in 2-second ‘microsleeps’. The things we do to combat fatigue – caffeine, loud music, open car windows – have no effect whatsoever on the incidence of microsleeps. None.
Your doctor doesn’t know. Academics do. Top sports coaches know. Some big companies, such as Google, know. But our doctors were trained before this knowledge was won. Worse, they were trained in hospitals, working long shifts. They think sleep deprivation is normal.