The key to your health is to know how many hours of sleep you need.
Three is almost never the magic number when it comes to sleep, despite what some presidential candidates, politicians and history’s so-called short sleepers would like us to believe. However, in order to be in good health you must know how much sleep your body needs.
Sleep medicine scientist and author of The Complete Guide to a Good Night’s Sleep (MacMillan) Dr Carmel Harrington says only one to three per cent of the population have a short sleep gene which means they only need about five to six hours sleep. Population studies show most adults need seven to nine hours. And a similar percentage of people have a long sleep gene and need 8-10 hours sleep.
Short sleepers are often referred to as “elite sleepers” while being a long sleeper is not something most people like to own up to.
“Personally I do not like the term “elite” as it may suggest an aspirational goal, something that one can achieve if they try hard—and this is not the case,” says Dr Harrington who is the managing director of Sydney sleep clinic.
“I also think it is very important though to distinguish between true short sleepers and people who actually need seven to nine hours of sleep but force themselves to get by on less, which is much more common to encounter.”
Research shows that true short sleepers tend to be more optimistic and energetic, often hold more than one job and there is a suggestion of subclinical hypomania. They are also thinner than average—even though sleep deprivation usually raises the risk of obesity. And they also seem to have a high tolerance for physical pain and psychological setbacks.
Dr Harrington says while presidential candidate Donald Trump claims he only needs three to four hours sleep, his behavioural characteristics suggest otherwise. “From a sleep researcher’s point of view he appears to have the cognitive and performance deficits consistent with lack of sleep—slow thought processes, a tendency for errors and flawed judgments, mood swings and irritability,” she says. “Moreover he is obese and we know that sleep deprivation increases the risk for obesity by 50 per cent. So I am not convinced that he is a true short sleep. More likely he is one of those people who needs (and would benefit from) seven to nine hours sleep but who forces themselves to get by on four hours.”
“As for Hillary, her latest health scare—pneumonia—suggests she should be spending less time on the campaign trail and more time asleep.”
According to historical accounts, Benjamin Franklin, Thomas Jefferson and Leonardo da Vinci were too busy to sleep much. Margaret Thatcher, Bill Clinton and Kevin Rudd also claimed to need little sleep. “Winston Churchill and Thomas Edison are often nominated as short sleepers but they were famous for their naps,” says Dr Harrington. Indeed, because Churchill was required to direct a global war campaign he actually slept wisely as he would regularly take two to four hour sleeps throughout the 24 hour period. In fact he probably slept close to eight hours in any given 24 hour period.”
Dr Harrington says our sleep need is physiological and largely determined by genetics, so if your mother/father needed eight hours’ sleep then chances are you will need that amount as well—and if you need eight hours then cutting back on sleep will just result in health, performance and cognitive deficits.
“It is an individual measure and you might need 7.5 hours and I might need 8.5 hours—the important thing is that you know what your magic number is,” says Dr Harrington.
She says we can become sleep deprived when we get an hour less than we personally need. So while we may be getting six hours a night, if we need eight or nine hours then we may experience the effects of sleep deprivation.
“If this happens for just one or two days then there are no ill-effects,” Dr Harrington says. “Studies have shown however that if sleep deprivation continues for more than 10 days there are cognitive and performance deficits. One can be chronically sleep deprived in the short-term, say one week to a few months, or in the long term, more than six months.
The signs of sleep deprivation are easy to spot. If it’s only mid afternoon and you are finding it difficult to stay awake in a meeting or a comfortable chair; if your eyelids are closing, you are yawning and you’re fighting it—then you’re sleep deprived.
Dr Harrington says sleep deprivation also makes us more likely to succumb to cold and flu infections. “This is because our immune system fires up during sleep and effectively rids our body of any virally infected or cancerous cells and if we aren’t getting the sleep we need the body cannot do this effectively,” she says.
“Sleep is also linked to how well we think and act and so when we are sleep deprived not only do we feel extremely tired, but we are prone to be more irritable and impatient, more stressed and more prone to mood swings, and after a night of bad sleep we don’t think very well.”
Regularly not getting enough sleep or sleeping poorly over long periods can have serious long term consequences. We are more likely to develop depression, three times more likely to experience cognitive decline with age and our chances of developing dementia are doubled,” Dr Harrington says. “The risk of obesity increases by 50 per cent and the odds of developing cardiovascular disease and metabolic disease such as Type 2 Diabetes are also much greater.”
Dr Harrington stresses that lack of sleep is not a badge of honour. “We need to remember that sleep is vital to our physical and mental health,” she says. “It nourishes us and repairs and restores our body. It allows us to meet the demands, challenges and joys of our day, and if we feel, more often than not, that we are not able to do this, then we need to look to our sleep.”