New American research has found that as many as one in 300 of us may have a natural preference for going to bed extremely early, and waking up fresh and revitalised in the small hours of the morning.
Led by University of California, San Francisco, along with the University of Utah and University of Wisconsin-Madison, the new study looked at 2,422 patients attending a sleep disorder clinic over a nine-year period to investigate the prevalence of advanced sleep phase.
People with advanced sleep phase have a body clock, also known as circadian rhythm, which is set much earlier than most.
The condition is defined by an ability to fall asleep before 8:30pm and wake before 5:30am, regardless of any occupational or social obligations, and having only one sleep period per day, meaning no naps.
Other criteria include setting this sleep-wake pattern by the age of 30, not using any stimulants or sedatives, no bright lights to help with getting up early, and no medical conditions that may impact sleep.
The condition is also not to be confused with the early rising that develops with normal ageing or the early waking experienced by people with depression.
“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,” says the study’s senior author Dr Louis Ptacek.
“These extreme early birds tend to function well in the daytime, but may have trouble staying awake for social commitments in the evening.”
To assess whether they may have the condition, the patients were asked about their medical histories and past and present sleep habits on work days and work-free days, while their levels of melatonin, blood oxygen, heart rate and breathing were measured, among other things.
The findings, published in the journal Sleep, show that 12 of the patients met initial screening criteria for advanced sleep phase.
As four of the 12 did not want to enroll in the study, this meant that the final eight patients comprised 0.03% of the total number of patients, which became one out of 300 when applied to the general population.
Until now, the condition was thought to be very rare.
The researchers add that this figure may be a conservative one, as the four patients who did not want to participate may have met the criteria for advanced sleep phase.
There may also be advanced sleepers who were not included in the study as they had no reason to attend the sleep clinic.
“Generally, we find that it’s 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,” says Dr Ptacek. – AFP Relaxnews