IF you are one of those people who is tucked up in bed by 8pm and can’t seem to sleep in after 4am you might not be as unique as you think. Scientists have discovered that sufferers of what is called “advanced sleep phase” are more common than previously believed.

In people with the condition, their circadian rhythm is disrupted by an early release of the sleep hormone melatonin, along with a shift in body temperature.

Distinct from earlier rising with age or early waking due to depression, researchers believe at least one in 300 people have the condition but the figure could be a lot higher. Scientists from University of California San Francisco, writing in the journal Sleep, say that people with advanced sleep phase do get a good sleep.

Dr Louis Ptacek, professor of neurology at the UCSF School of Medicine said: “While most people struggle with getting out of bed at 4am or 5am, people with advanced sleep phase wake up naturally at this time, rested and ready to take on the day.

“These extreme early birds tend to function well in the daytime but may have trouble staying awake for social commitments in the evening.

“Advanced sleepers rouse more easily than others and are satisfied with an average of an extra five-to-10 minutes of sleep on non-work days, versus the 30-to-38 minutes more sleep of their non-advanced sleeper family members.”

Along with colleagues from the universities of Utah and Wisconsin, the team looked at data from a nine-year study at a sleep disorder clinic that reviewed 2,422 people. Of those, they ruled out 674 who suffered from sleep cycle problems and identified 12 in the remaining 1,748 who had advanced sleep phase.

However four of those declined further tests, leaving the team with 0.03 per cent of the total patients with the condition. But they believe the figure should be higher because many sufferers would not bother to go to a sleep clinic.

Mr Ptacek said: “Generally, we find it is the people with delayed sleep phase – those night owls that can’t sleep until as late as 7am – who are more likely to visit a sleep clinic. They have trouble getting up for work and frequently deal with chronic sleep deprivation.” Participants in the study had their sleep logged and melatonin, oxygen, brainwave, heart rate and breathing levels tested. Mr Ptacek added: “We hope the results of this study will not only raise awareness of advanced sleep phase but also help identify the circadian clock genes and any medical conditions they may influence.”