How much sleep do you really need?

In her friendship group, PR director Renae Smith is known as the granny.

Her need for 10 hours of sleep every night doesn't just affect her social life; it also affects her professional life: "If I don't get 10 hours or more, I'm exhausted. At 2.30pm I get really sleepy and my eyes get itchy," she says.

"If I haven't had 10 hours, my patience and concentration are affected – I have a shorter fuse and get frustrated at receiving too many phone calls or if my emails back up."

On a weekend, the 32-year-old averages 11-12 hours. She's in a breed of professionals who need longer than the requisite 7-8 hours to operate effectively.

It has been a problem all her working life: "I remember working in an office a few years ago and after lunch I'd sometimes lay down on my desk and take a 20-minute nap if I hadn't had my 10-plus hours the night before."

Sleeping more than nine hours can be as harmful as not getting enough sleep.

Clarissa Hughes

Long sleepers

Short sleeping is well documented. Recent research conducted by the Centre for Applied Genomics in Philadelphia found that a small proportion of the population can operate on fewer than five hours per night.

Further evidence suggests one per cent of the population survive on very little sleep because they're used to being chronically sleep deprived – they've been named "short sleeping elite" – a club that famously features leaders such as Barack Obama, Margaret Thatcher and Winston Churchill.

Long sleepers, however, seem to suffer from a lack of research, and perhaps unfair stereotypes that they're lazy, sedate or not very rock n' roll.

For Suzanne Jones, her unusual sleeping habits came from her job: "I was a newsreader on Melbourne radio for 13 years, eight of those years were on the early breakfast shift, so I had to train myself to get enough sleep to function. I can fall asleep within 20 seconds of closing my eyes and I'm in a deep sleep. It amazes those over the years that have shared the night with me. I need my sleep otherwise I have to spend at least one of the days in the weekend to catch up if I don't get my nine hours a night."

Too much of a good thing

Sleep expert Clarissa Hughes suggests that this type of sleep habit could actually be damaging: "There's a body of evidence that suggests that sleeping more than nine hours can be as harmful as not getting enough sleep. Scientific evidence is suggesting 6.5 to 8.5 is optimal for health. That said, we're all individuals and we'll adapt to a certain extent to the sleep schedules we adopt."

The founder and CEO of the Resilience Institute, Stuart Taylor, says power naps should be a maximum of 15 minutes after lunch. Catching up on sleep isn't a total myth, but sleep debt is better discharged by sleeping early as opposed to laying in.

In this sense Smith, from Newtown in Sydney, is following the rules pretty well. "I have rules around my napping," she says. "I never sleep later than 3pm, and 2.30pm is ideal. I don't drink coffee after lunch time, which I find has helped. I take valerian root at night, as well as magnesium, which seems to help me have more of a restful sleep.

"The main thing for me, though, is my pillows – without the right pillows and some extra ones to support my shoulders and hips, I can't sleep. So this is a huge thing for me, especially when I travel."

The long-sleeping professional, then, does exist – but the short-sleeping elite is the preferable club: "If I could take a pill to be like that, I would," Smith admits.

Five sleep myths busted

Sleep expert Clarissa Hughes nominates some misconceptions about snoozing. 

You can make up for lost sleep in the week by sleeping in on weekends

Although this sleeping pattern will help relieve part of your sleep debt, it will not completely make up for the lack of sleep. Also, sleeping later on the weekend can affect your biological clock so that it's much harder to go to sleep at the right time on Sunday night and get up early on Monday morning.

Your body adjusts quickly to different sleep schedules

It can take more than a week for your body clock to adjust after travelling across several time zones or switching to night shifts.

Gym bunnies need more sleep

There's nothing to suggest that people who exercise need more sleep. Exercise is great for improving the quality of sleep if it's not done too close to bed time. But people who exercise should make sure they get adequate sleep, as any muscular wear and tear repairs best when we get good sleep.

Milk before bedtime helps you sleep

It's an old wives' tales, but also a truism. To help us fall asleep, foods that are good sources of tryptophan - a sleep-inducing amino acid - help the body make serotonin and melatonin, the 'body clock' hormone. These include walnuts, dairy products and honey.

One hour of sleep before midnight is worth two after

Another total myth. Sleep is sleep.

How much sleep do you need to be at your best? Let us know in the comment section.