A handful American adults are genetically programmed to wake up before dawn and go to sleep at 8pm – and new research suggests it may be more common than previously thought.
The routine is actually a condition called ‘advanced sleep phase’, has long been considered incredibly rare.
But according to a new study by researchers at the University of California, San Francisco, it seems to be a genetic quirk that affects one in 300 adults – which would equate to around 800,000 Americans.
Those affected have body clocks (‘circadian rhythms’) that operate earlier than most, which triggers strong releases of melatonin, the hormone which makes us sleep, in the afternoon.
While most of us start waking up earlier as we age, and many people with depression wake up at night, this phenomenon is different, the researchers explain.
Some people naturally wake up much earlier than the rest of us (file image)
Uniquely, though the rest of us relish – and require – about 40 minutes extra sleep on non-work days, advanced sleep phasers are fine with five or 10 minutes more, or no extra time at all, to still function at their peak.
Their only issue is staying awake at night, which can make after-work socializing complicated.
To study the phenomenon, UCSF researcher Dr Louis Ptacek, along with colleagues at the University of Utah and the University of Wisconsin, studied 2,422 patients at a sleep disorder clinic over nine years.
That proved slightly problematic because advanced sleep phasers are unlikely to visit a clinic: though they do battle with an unusual sleep cycle, it doesn’t tend to affect their waking hours in the same way that people who sleep chronically late (i.e. up until 7am) suffer.
However, they did find 12 people who met screening criteria for advanced sleep phase, based on sleep logs, tracking the level of melatonin in their saliva, recording their brainwaves, oxygen levels in the blood, heart rates and breathing.
Four of the 12 didn’t want to be part of the study. The remaining eight made up 0.03 percent of the total number of patients – or one out of 300.
That was how the team came up with the idea that, in the general population, around one in 300 adults suffer from advanced sleep phase.
It is an imperfect measure, they concede. In reality, Dr Ptacek believes, the figure is much higher.
They found, through interviews and screenings with each of the patients, that all of the eight had relatives with the same condition.
Through genetic testing, they found that two of them had genes linked to advanced sleep phase.
‘We hope the results of this study will not only raise awareness of advanced sleep phase and familial advanced sleep phase,’ said Ptacek, ‘but also help identify the circadian clock genes and any medical conditions that they may influence.’