Most adults require between seven and nine hours' sleep a night to remain healthy, but research has found some people can survive on much less without suffering detrimental health effects.
A rare gene mutation that allows people to thrive on minimal sleep may also be linked to a superior ability to remember things. Photo: 123RF
Dr Ying-Hui Fu, a professor of neurology and a pioneer in the study of sleep and genetics at the University of California San Francisco, has identified a number of gene mutations that control how much sleep people need.
Her research revealed that people she termed 'natural short-sleepers' benefit from a gene mutation that enables them to lead healthy lives despite requiring only four to six hours' sleep a night.
Professor Fu told Sunday Morning the mutations were new, from an evolutionary point of view, and were likely a response to quite recent technological innovations.
"Our sleep behaviour significantly changed because of the lightbulb and electricity, which enabled us to stay up much later," she said.
"Before [those inventions] there was no advantage to staying up late."
Natural short-sleepers were "pretty rare", Fu said.
They tended to be active and healthy and didn't rely on coffee or other external stimulants to keep them awake despite their reduced sleeping hours.
"From what we've observed over the last 15 years, [natural short-sleepers] seem to remain very healthy."
Fu's research involved manipulating the genes of mice to reflect the short-sleep gene mutation she had identified in humans.
"It takes about a year or two to make a mouse model that carries exactly the same mutation as a human," she explained.
Once this was achieved however, she was able to show that the mutant mice exhibited the same short-sleep behaviour as humans with the same mutation.
This modelling also revealed other possible effects of the mutation which human participants in her study had alluded to, including a superior ability to remember things.
"Some of them (the human short-sleepers) will tell me that they have these really amazing memories ... they can speak many languages, or they hear something once and they never forget it," Fu said.
"What we found is that in the normal mice - like normal humans - if we don't sleep well that night, we actually don't remember what we learned during the day as well as if we just get a good night's sleep...
"We found these mutant mice ... we can sleep-deprive them and they still remember everything very well, while the normal mice ... if you sleep-deprive them, they don't remember what they learned the day before."
A second group Fu's research identified were people who slept for shorter than the recommended amount of time but who didn't possess the natural short-sleeper mutation.
These 'habitual short-sleepers' were people who had trained themselves to survive on less sleep, but Fu warned their actions were detrimental to their health.
"If I need eight to eight-and-a-half hours of sleep and I just try to sleep six hours ... very quickly I would be performing at 70 percent ... at best, of my capacity.
"I can live like that for years, but it's really not good for me ... the problem is, most people don't realise that."
Fu acknowledged there were advantages to being able to survive on fewer hours' sleep in the digital age and said it was likely more humans would eventually evolve to become natural short-sleepers.
In the meantime, her aim is to understand how and why the short-sleeper mutation allows its possessors to sleep more efficiently.
"When we are sleeping, our body actually is very busy doing all kinds of things ... whether it's getting more energy for the next day or removing toxics that we accumulate in our body ... all this our body needs to do while we are sleeping and for us it takes eight hours but for [natural short-sleepers] it takes four to six hours."
"We're trying to figure out how it works; how it is that their sleep is more efficient, so we can help everybody sleep more efficiently."
