Most people don't know they've got sleep apnoea until a bed partner hears them stop breathing in the night.
The frightening condition affects more than one million Australians and unchecked, can shorten life expectancy.
New research by Neuroscience Research Australia is shedding light on this mysterious condition and showing there's no one-size-fits-all approach to treatment.
Study author Danny Eckert tells The Huffington Post Australia everything you need to know about sleep apnoea.
What is sleep apnoea?
"It's a very common disorder affecting more than one million Australians where essentially, the throat area closes again and again throughout the night," Eckert said.
"In severe cases, the throat closes 100 times per hour. People can stop breathing for anything from 10 seconds to over a minute.
"As you can imagine, when you're not getting air through, oxygen levels go down, there's a stress on your heart from creating a suction pressure in the lungs and what usually happens is people wake up for five to 10 seconds.
"They're mostly not aware of waking up."
Can it be dangerous/harmful?
Eckert said it had serious effects on all areas of life.
"People who have untreated sleep apnoea are seven times more likely to be involved in a car crash," he said.
"Every single organ in the body is affected by untreated sleep apnoea. It increases the risk of cardio vascular disease, it increases the risk of neurocognitive impairment so not being able to think clearly, you're more likely to be depressed and have mental health issues. Your immune system is more likely to be suppressed.
"There's even recent data showing untreated people are more likely have cancer."
How is it diagnosed?
"It can be difficult because these things creep up on you. People don't tend to wake up one day with sleep apnoea. Perhaps they put on weight over time, or get older and ageing throat muscles are less effective.
"Typically bed partners are key in the whole process. It's associated with loud snoring which can be disruptive but more distressing is when a bed partner witnesses their partner stop breathing -- it can be quite scary."
As for single people, Eckert said there were telltale signs something was wrong.
"Those who don't have bed partners may feel very tired, have headaches and feel unrefreshed after sleep," he said.
"They also might find themselves falling asleep at unwanted times."
Who does it affect?
Eckert said men were more likely to get it than women and people often developed it in middle age or after weight gain but that didn't mean young, fit people were immune.
"Obesity is a major risk factor for sleep apnoea -- that's well appreciated in the literature -- but our new data [published in the Journal of Clinical Sleep Medicine] shows that's possibly overemphasised.
"More than half the people treated at our sleep lab for sleep apnoea were in a healthy weight range."
Does it affect children?
Eckert said it was often disruptive for children but there was an effective treatment.
"As opposed to being sleepy, children with sleep apnoea is associated with behaviourial issues," he said.
"It's not as common as it is in adults and it's quite a different disorder.
"It tends to be caused by the adenoids and tonsils being too large for their airway while they're growing, and the main treatment is to remove the tonsils and adenoids."
What treatment is available for adults?
He said the first line of therapy in adults was developed in Australia in the 1980s.
"It's called continuous positive airway pressure (CPAP) and it involves wearing a mask to bed attached to a small device that blows air in as you breathe," he said.
"It completely transformed the field of sleep medicine but overall it's probably only effective in half of all patients who try it."
He said the second line of therapy was a mouth guard that brought the jaw into alignment and surgery was beneficial for some.
"Right now we're not very good at determining whether a mouth guard or surgery will work well ahead of time," he said.
"In my lab we're trying to figure out how to target each specific cause of sleep apnoea with new clinical treatments.
"Clearly the one-size fits all approach isn't working."