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How much sleep do you need? I have a Four Hour Rule... but science says it's not healthy

Insomnia Diaries

Insomnia Diaries is a column by Miranda Levy in which she shares her experiences of the chronic sleep problems she has experienced over the past decade and a half. It is published every Monday at 12pm 

I have something called the Four Hour Rule. It’s the insomnia version of the The Five Second Rule – the hygiene ‘excuse’ that states it’s OK to use food or cutlery that’s been on the floor so long as it’s picked up within five seconds.

After years of suffering from poor sleep, I have worked out that four hours a night is my threshold between lunacy and lucidity. If I sleep more than four hours, I’ll be OK to get through the day; less, and I’m in trouble. It’s not a rule that’s set in stone – four hours still leaves me tired; and if I’m on the four-hour borderline, I can wobble between cogency and incoherence – but it’s a useful barometer for how my day will progress.

The problem with my Four Hour Rule is that it can encourage a form of what has been termed ‘trackorexia’, where you become obsessed with counting your sleep achievements. For a while I’d jot down my numbers every morning, like an insomniac Bridget Jones, until I realised that that, in itself, was a ‘sub-four hour’ crazy thing to do.

So, is four hours enough to live healthily?

A look at the so-called ‘sleepless elite’ suggests it might even be positive. Margaret Thatcher was said to need only four hours a night; Donald Trump claims he gets by on roughly the same; and Napoleon Bonaparte, when asked how much one needs, is said to have replied: "Six for a man, seven for a woman, eight for a fool." Does that make me a superhero?

But these people are outliers. The received wisdom seems to be that you need a solid seven to eight hours for most of your life. According to a study last month in the American journal Experimental Physiology, 18-60 year-olds need seven to eight hours, 61-64 year-olds need seven to nine, and the over 65s drop an hour again.

“Why seven or eight hours seems to be the magic number is unclear,” said Christopher DeSouza, a professor at Boulder University, Colorado, and the author of the report. “But don’t underestimate the importance of a good night’s sleep.” Thanks Chris – as if I didn’t know.

And what of those of us who can’t manage the ‘magic number’? A quick Google of ‘how much sleep healthy’ yields 631 million results. The NHS website – perhaps a more useful starting point – quotes a 2010 study that was published in the peer-reviewed scientific journal Sleep, which found that less than six hours’ of sleep is associated with a 12 per cent increased risk of premature death.

Cheery stuff – but a closer look at the study, which was carried out at the University of Warwick, found that there’s a 30 per cent rise in risk for people who sleep nine hours or more, because they may have underlying medical or social problems.

The NHS website concludes there could be a relationship between poor sleep and early death – but also that different people need different amounts of sleep, depending on their age, lifestyle, diet and environment.

Of course, lack of sleep is not only a matter of life or death. There are grey areas in between, where a truckload of studies have shown that insomnia causes everything from weight gain to heart disease to premature Alzheimer’s (which I’ll return to in a future column.) And that’s before you even mention the way it crushes your general wellbeing.

A quick vox pop of the real world. A consultant psychiatrist I once saw (early 40s, I’d guess) told me he had five or six hours a night. My father, 76, goes to bed around 1am and is up at 5am. A twenty-something daughter of a friend swears by nine and a half. All seem to function perfectly well.

As for me, yes, I can function on four hours a night: I can speak, reason, cook, walk, write. But I am tired, occasionally grumpy and a bit impatient. I might snap at my nearest and dearest, then regret it later.

Oddly, I’ve learned that getting five or six hours (I even managed seven once) doesn’t leave me feeling much better. Perhaps I have built up a ‘sleep debt’ while battling insomnia for so many years – and maybe it will manifest itself somewhere down the track. I know my physical health is already suffering (but, again, more on that another time).

Ultimately, the amount of sleep you need to cope with a normal day seems to be such a subjective thing. So, tell me, what works for you?

Follow Miranda on Twitter @mirandalevycopy

Insomnia Diaries will appear on telegraph.co.uk every Monday at 12pm. Last week's column can be read here