People who sleep for less than six hours a night are more likely to die prematurely, according to a new study, but just how easy is it to meet the eight-hour quota in this day and age?
We all know the importance of a good night's sleep, or rather the effects of too little: tiredness, irritability and the overwhelming urge to climb back into the leaba in the middle of the day.
However, a slew of recent studies reveal that the effects of sleep loss are far more pernicious than a weary disposition and the tendency to take 20 minutes to find your car keys. In fact, the quantity and quality of sleep we get is inextricably linked to our long-term health.
In the most recent of such studies, a combined team from the University of Warwick, England, and Italy's Federico II University Medical School, analysed 16 studies involving 1.3 million people.
They discovered that people who slept for less than six hours each night were 12pc more likely to die prematurely -- before the age of 65 -- than those who slept the recommended six to eight hours a night.
Another study in 2004 linked sleep deprivation to obesity, finding that sleep loss alters the levels of hormones that regulate hunger and leads to an increased body mass index. It was found that those who reported less than four hours of sleep a night were 73pc more likely to be obese.
But how likely is it to get eight hours' sleep a night in an era in which we are working and commuting for increasingly longer hours? Just like the five-a-day fruit and veg quota and the two litres of water recommendation, is eight hours of sleep a number that we aim for but rarely hit?
According to Dan Smyth, of Irish Sleep Apnoea Trust, the optimum amount of sleep for adults is indeed seven to eight hours, however, he adds that it's a case of quality over quantity.
"If you get six hours of undisturbed, quality sleep, for instance, you're doing pretty well. Sleep is very structured and there are various stages which you must get through if you are to wake up feeling refreshed."
In the past, Smyth has spoken out about the lack of training GPs receive in sleep medicine and the scarcity of funding for sleep disorder clinics.
"Sleep is a massive area and it's only since the '60s and 70s that the medics have really got into it," he says. "We feel that sleep will become the medicine of the 21st century to cure all ills."
According to Smyth, sleep deprivation and sleep disorders are linked to everything from heart disease and stroke to lack of libido and decreased short-term memory.
"Say you go to your GP and he or she says you have high blood pressure -- that can be one of the first warning signs of an untreated sleep disorder."
He cites studies which show that where sleep apnoea is treated, blood pressure readings drop by as much as 25pc while the incident of stroke decreases by 33pc.
"It is our belief that it is time the health service . . . treated sleep disorders, particularly at an early age. If they did [patients] wouldn't have these problems in later life."
The subject of sleep disorders does open up a chicken and egg debate, however, as Professor Walter McNicholas, the president of the Irish Sleep Society and director of the Sleep Disorders Unit at St Vincent's University Hospital, is quick to point out.
"Chronic sleep deprivation is recognised as a contributor to poor health," he explains. "However, it could be related to poor lifestyle which can have adverse effects on one's health in general.
"It could be a reflection of another medical problem which is interfering with sleep, or a specific sleep disorder which adversely impacts on general health."
McNicholas considers a regular sleep pattern more important than the time one wakes up or nods off. "There are some who go to sleep early and get up early; some who go to bed late and get up late. The important thing is that one has a consistent night's sleep and an adequate duration of it for sleep to be restorative."
But what about those who shirk the eight-hour quota and claim to be functioning perfectly? Margaret Thatcher boasted that she only needed four hours of sleep a night. Thomas Edison said he averaged about four or five hours. In fact, we all know someone who brags about their limited time spent on the pillow.
Are they the exception to the rule? "No," says McNicholas firmly. "It's an exercise in self-delusion to think you can get by with three or four hours' sleep."
Smyth agrees. "Everyone carries a certain amount of what is known as 'sleep debt' and, like all debts, it has to be repaid," he explains. "If you have an excessive sleep debt, it is going to demand attention, particularly during the day."
The nation's chronic sleep debt has become a popular talking point in recent years, no doubt adding to the multi-million euro industry that is sleeping pills, aids and gadgets, which range from the practical to the completely nonsensical
An estimated 100,000 people in Ireland suffer from sleep disorders, yet most of them don't seek medical advice. Instead, they are inclined to self-medicate and self-diagnose, which potentially exacerbates the problem.
With quality sleep so critical to long-term health, it pays to discuss sleep disorders with a professional.
Irish Sleep Society; www.irishsleepsociety.org
Irish Sleep Apnoea Trust; www.isat.ie