Katie Byrne: Sleeping for just five to six hours a night? It’s highly likely that you’re chronically sleep deprived
As someone who needs at least eight hours of sleep to get through the next day without slurring my words, I've always been dubious of people who claim they can spring out of bed after just five to six hours of slumber.
As a general rule, they tend to be high-achievers: CEOs who complain about there not being enough hours in the day; tech entrepreneurs who spout off chest-thumping catchphrases about sleeping when they die and lifestyle bloggers who get up at crazy o'clock to work out.
I've always suspected that these short-sleeping early-risers were in fact chronically sleep deprived, but it wasn't until I finally got around to reading Matthew Walker's brilliant Why We Sleep that I began to understand just how devastating the effects of chronic sleep deprivation can be.
Walker, a Professor of Neuroscience at UC Berkeley, doesn't mince his words.
"Routinely sleeping less than six or seven hours a night demolishes your immune system; more than doubling your risk of cancer," he writes in the opening chapter.
Insufficient sleep is a key lifestyle factor determining whether or not you will develop Alzheimer's disease, he adds. It also disrupts blood sugar levels so profoundly that you would be classified as pre-diabetic.
If that hasn't made you rethink your 7am spinning class, there's a mental health toll too.
According to Walker, inadequate sleep contributes to all major psychiatric conditions, including depression, anxiety and suicidiality. Like I said, he doesn't mince his words...
The author, who also works as a sleep scientist at Google Life Sciences, goes on to describe sleep as the "single most effective thing we can do to reset our brain and body health each day". It's a rousing statement but the trouble is that it might not get through to those who believe they have a superhuman ability to sleep less than everyone less.
Yes, there is a genetic abnormality that allows a tiny percentage of people to get by on five and a half to six hours of sleep a night - but before you decide that you must be in this cohort, Walker points out that you are far more likely to be struck by lightning in your lifetime than to carry this genetic mutation.
As for those who can get by on five hours sleep or less a night without showing any signs of impairment? According to studies, the total number of people with this superhuman ability is zero.
And still we minimise the effects of chronic sleep deprivation. Just look at the chalkboards outside coffee shops and it won't be long before you see a sign that celebrates the effects of caffeine on existential exhaustion.
Caffeine is not a food supplement, continues Walker. Rather, it is "the most widely used (and abused) psychoactive stimulant in the world".
The scientist explains how caffeine "blocks the sleepiness signal" that is normally communicated to the brain by adenosine, a chemical that increases the desire to sleep.
The longer you are awake, the more adenosine accumulates. Well, until you introduce caffeine, that is.
Walker says drinking caffeine when you're tired is "the equivalent of sticking your fingers in your ears to shut out a sound", before citing studies which show that a person who has a cup of coffee after their dinner at 7.30pm will still only be half way toward completing the job of cleansing their brain of caffeine at 1.30am.
Inadequate sleep also contributes to weight gain, he says. When a person is sleep deprived, the hormone that makes us feel hungry spikes while the hormone that signals food satisfaction is suppressed.
"Worse, should you attempt to diet but don't get enough sleep while doing so, it is futile, since most of the weight you lose will come from lean body mass, not fat," he adds.
Why We Sleep presents some astonishing research, but before you invest in the book, it might be worth answering some of the questions that Walker asks to ascertain if a person is sleep-deprived:
⬤ After waking in the morning, could you fall back asleep at 10 or 11am?
⬤ Can you function optimally without caffeine before noon?
⬤ If you didn't set an alarm clock, would you sleep past that time?
⬤ Do you find yourself at your computer screen reading, then rereading (and perhaps rereading again) the same sentence?
⬤ Do you sometimes forget what colour the last few traffic lights were while driving? (The scientist adds that distraction is often the cause but lack of sleep is "very much another culprit")
Walker also recommends the SATED questionnaire - a simple five-item scale that assesses sleep health (you can find it online).
If your answers reveal that you're sleep-deprived, then this is a book that you should probably read - preferably while under a duvet.
Health & Living