For 12 years Karen McFarland was woken throughout the night by a weird sensation of electricity building up in her legs, and an overwhelming urge to get up and move them.

Key points: Restless legs syndrome affects senses and movement and is characterised by an urge to move the legs and uncomfortable sensations

Restless legs syndrome affects senses and movement and is characterised by an urge to move the legs and uncomfortable sensations We don't know what causes restless legs but scientists think it could be linked to iron or dopamine levels in the brain

We don't know what causes restless legs but scientists think it could be linked to iron or dopamine levels in the brain Medication for restless legs is only prescribed in severe cases, but there are things you can do to relieve mild symptoms

It wasn't an unusual case of sleepwalking or an irritating skin condition disturbing Ms McFarland's sleep — she has what's called restless legs syndrome.

She first experienced it during the last trimester of her first pregnancy, and no-one knew what it was.

"I talked to my obstetrician, who just looked at me quizzically and thought I was a bit loony," she said.

The restless legs went away after she gave birth, and then came and went again during her second pregnancy.

"I just thought: that was horrible, but now it's gone.

"But then it came back with a vengeance when I was about 45, completely out of the blue."

And with night after night of little to no sleep, it started to impact on her job as a midwife.

"I had to drop from full time to three days a week because I was so sleep deprived," she said.

Like many people who suffer from restless legs syndrome, Karen McFarland had no idea what it was for a long time and so didn't seek help. ( Supplied: Karen McFarland )

What is restless legs syndrome?

Restless legs syndrome is a sensorimotor disorder, which means it affects both your senses and movement.

"People have the sense of needing to move their legs, usually worse at night, and these symptoms improve if they can get up and move around," said specialist sleep physician David Cunnington of the Melbourne Sleep Disorders Centre.

Other symptoms include feeling pins and needles in the legs, heaviness, or even creepy-crawly sensations under the skin.

"There's no end to the different sensory ways people experience restless legs — whether it's heaviness of the legs or pins and needles or something else," said Dr Cunnington.

Symptoms can range in severity from uncomfortable to painful, and relieving them is what motivates the restlessness, whether it be pacing, or tossing in bed, or even jumping on an exercise bike.

"It's also made worse if they're forced to sit still — like on a plane or at the movies," Dr Cunnington said.

Pregnant women in the second or third trimester, women and older people are more likely to get restless legs syndrome. ( Getty Images: David Pereiras/EyeEm )

But it's not the same as feeling fidgety or restless which everyone experiences from time to time if you're bored or have been sitting still for too long.

"It's the timing and the situation of the symptoms that really makes the diagnosis," Dr Cunnington said.

"It gets worse when you sit still, and better when you get up, and it's predictably worse in the evenings."

And if you twitch and jerk your legs during sleep but don't have other symptoms, you probably have periodic limb movements rather than restless legs syndrome.

Restless legs, sleepless nights

One in six people will have experienced the symptoms of restless legs at least once.

But severe cases where daily medication is needed to manage the symptoms only occurs in about one in 100 people, according to Dr Cunnington.

The more severe cases tend to be when someone gets symptoms throughout the night, every night, which then has a big impact on sleep and fatigue.

If you wake up throughout the night from tingling in your legs, or you regularly get up to move your legs, it's likely you're not getting enough sleep.

And we know poor sleep can be associated with health issues including heart disease and diabetes, as well as leading to mental health problems.

Situations where you're forced to stay still, like on a plane or in a movie, can make the symptoms of restless legs worse. ( Getty Images: Radius Images )

When Ms McFarland's restless legs symptoms started up again she tried different remedies she'd read about, but nothing worked until a fellow midwife showed her a research paper about the syndrome.

"That was the first time I'd ever read about it — and it had a name."

"I learnt about a medication that was approved for restless legs syndrome, so I asked my doctor if I could try it. And it worked."

But for most people with restless legs syndrome, treatment is complicated and doesn't always work — partly because we know so little about the disorder.

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The actual cause of restless legs syndrome is yet to be found, said Brendan Yee, an associate professor at the Woolcock Institute of Medical Research and a respiratory and sleep physician.

"We think it may be related to an iron transport issue within the brain," Dr Yee said.

"A lot of patients who have iron deficiency have an increased risk of developing restless legs. And when you get their iron levels back up the restless legs goes away."

There is also a potential link to the brain chemical dopamine, which is important for movement.

"There may also be some problems with dopamine signalling, and some people have found dopamine treatments to be quite useful," Dr Yee said.

"I think those two [dopamine and iron] are probably important in terms of the mechanism behind restless legs."

There may also be a genetic component to getting restless legs syndrome.

"If you've got a family member with restless legs that makes your risk higher, but there's no biomarker that we can measure and say that you're going to get it," Dr Yee said.

How do deal with the symptoms

For people with severe symptoms it's best to discuss treatment options with your GP, said Dr Cunnington.

"Drug therapy for restless legs syndrome does get reasonably complex and we often have to keep reviewing people to manage either side effects or worsening symptoms over time," he said.

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If you only get mild symptoms, or only experience them occasionally, there are other things you can do to ease the discomfort, Dr Cunnington said.

"Obviously you can get up and move around, or another option is to change the temperature of your legs," he said.

"Putting your legs in a warm bath, or hanging feet out the end of the bed to make them cold usually will settle down restless legs symptoms."

There is some evidence that cutting down caffeine, alcohol and nicotine can also reduce restless legs symptoms.

But while there is anecdotal support for magnesium supplements, the scientific evidence is inconclusive.

Dr Yee thinks there may be a strong placebo effect to taking magnesium because the symptoms of restless legs syndrome are so individual.

With increasing awareness around sleep health, or the lack of it in Australia, more people have heard about restless legs syndrome, but Dr Yee said some health practitioners still find it confusing.

"Because we don't have great diagnostic tests, because we don't have great animal models of the syndrome, there's still a little bit of scepticism about it," he said.

"I think it's only when you start seeing patients that actually have restless legs syndrome that you realise this is a potentially very nasty and troublesome condition."