Therese Rein suggested in a SMH article on the weekend that the PM, Kevin Rudd, only needs “about three hours of sleep a day”. The interviewer, like most of the rest of us, seemed sceptical that the PM could function effectively on this amount of sleep on a regular basis.

If we look at what the PM’s wife said in detail, she actually said:

Kevin starts at around six in the morning he might get to bed around one or two, or maybe three. He doesn’t need a lot of sleep.

The claim to get by on very little sleep is very common amongst high performing professionals, although rarely as true as they would want us to believe.

The PM’s wife suggested Kevin typically goes to bed between 1am and 2am and sometimes as late as 3am and rises at 6am. That is, he gets four-five hours sleep most nights and occasionally as little as three hours — a common pattern in highly driven busy professionals. The most interesting element of this statement is the desire to emphasise the infrequent and to exaggerate the level of sleep loss actually experienced.

The reasons behind why high performing people like to underestimate their sleep are complex. It’s based on our cultural biases about the type of personality we attribute to sleep durations and sleep. Despite a large body of scientific evidence to the contrary, people typically attribute laziness and lack of motivation to individuals who express a high sleep need and/or report long sleep durations.

The reasons for this are steeped in our cultural and religious views of sleep. Since the rise of Protestantism in the 15th century, sleep has been considered an “appetitive behaviour like food and sex. Moral goodness comes from the ability to resist the temptations of the flesh. In the 16th century, one pursued celibacy and fasted in order to find God and go to heaven. In the 21st century, where celibacy and fasting are well nigh impossible, we deprive ourselves of sleep to prove our “goodness” and suitability for a place in the new heavens of government and corporate boardrooms.

The converse is also true. Short sleepers are typically considered to be more dynamic, more likely to succeed and more likely to be higher performing individuals. Nothing could be further from the truth. The scientific research clearly indicates that once long-term sleep falls below an average of five-six hours per day, cognitive impairment and negative long-term health consequences are inevitable.

Nearly all individuals deprived of two- three hours of sleep per night over a week will show impaired brain function with a level of functioning equivalent to a blood alcohol concentration between 0.05-0.08%. Similarly, the majority of people when reduced to an average sleep duration of four hours per night or less will become irritable, subject to emotional outburst and will engage in stereotypical thinking and language.

There are however, considerable differences between people in their susceptibility. As with alcohol intoxication, people impaired by sleep loss may be unaware of the impact of sleep loss and/or lack insight into the performance decrements they are experiencing. There is no doubt there are a very small group of people who report being habitually short sleepers and who report “getting by” on less sleep than others. Whether this is actually the case or they are basing their judgment on self-deception is less clear. When measured objectively, most of those self-reporting short sleep or resilience to sleep loss fail to demonstrate this in laboratory based tests of sleepiness or performance.

The key point to understand in this debate is that many people, irrespective of the facts, like to promote the idea of themselves as “short sleepers”. They do this in order to promote the idea that they are hard working, motivated and more likely to succeed. There are many famous examples of politicians and business leaders who actively promoted the idea of themselves as short sleepers including Winston Churchill, Ronald Reagan, Margaret Thatcher, Bill Clinton Thomas Edison and Bill Gates.

While it is true that these individuals often had short night sleeps, they were also renowned “nappers” who would catch up on sleep during the day while travelling in trains, planes and automobiles or between meetings. When their total sleep for the 24h period was summed it was not as low as was frequently claimed. These individuals had adopted what is commonly referred to as a split-sleep or polyphasic sleep strategy.

No-one doubts the value of hard work and the commitment of many busy professionals to making the world a better place. The problem arises from our failure to discriminate between “more is better” and “enough is enough”. While reducing our sleep in order to increase the time available for good works is an admirable sentiment, the scientific evidence is unequivocal. There is a point of diminishing returns.

If we push the system too far and fail to sleep enough, the short-term benefits are outweighed by the long term consequences in terms of poor health and impaired decision making. Ultimately, if you don’t get a good nights sleep over the long-term then you are likely to be a grumpy and irritable person, make bad decisions and put yourself, family and community at risk.

Professor Drew Dawson is Director, Centre for Sleep Research, University of South Australia.