How many hours of sleep is the perfect amount

I've got three, actually: hammock on a sunkissed beach in Bora Bora; in the warm embrace of Chris Hemsworth and anywhere soft after certain quantities of rum.

Let me rephrase that. What's your ideal amount of sleep?

I'll take as much as I can get. But something tells me you already know the answer.

Indeed I do. And it's less than you'd expect. For some time, we've all been told that eight hours is the magic number for slumber. Eight keeps you healthy, happy and energised - or so we thought.

According to a new American study, eight is too much.

Researchers recruited 100 elderly people, tracked their sleep and tested them for alertness and cognitive ability. They found that sleeping more than seven and a half hours was linked to decreased brain function.

So what's the sweet spot? Please don't tell me it's brutally short. Donald Trump says he only needs four hours, and I'd suggest that speaks for itself.

The study concluded there's a good middle range: between five and a half and seven and a half hours a night.

I guess that's what most of us can expect now we're all heading back to the office.

But you shouldn't have too little sleep, either.

Other studies have shown that sleep helps protect your brain by flushing away the toxins it produces while it's working all day. And during sleep, the brain also produces proteins that fight infection and inflammation - crucial for peak immunity.

It's not easy to hit a sweet spot. Especially if you're jolted awake throughout the night by your baby, snoring partner or the day's anxieties getting all up in your land of nod. Any tips?

A bath is proven to help you fall asleep faster. And experts say that if you wake up in the night, don't lie there fretting - get out of bed and sleep will return faster when you're back beneath the covers.

Natural fibres and a temperature of around 18 degrees help. A consistent bedtime is essential to sleep quality, and you should wind down at least an hour before by ditching the screens, dimming the lights, and trying to relax.

Ah, then I'll need the rum, the hammock and the Hemsworth after all.