This means they are out of sync with daily rhythms
Most of us love a good lie-in on the weekends. But for some people, getting out of bed each morning is a daily struggle that can disrupt their lives.
Now, researchers believe they have found out why some people struggle to sleep at night and reach for the snooze button in the morning - their body clocks are set too slow.
A team from Flinders University in Adelaide, Australia, are investigatingdelayed sleep phase disorder, which is characterised by a persistent inability to fall asleep and wake at a conventional time.
Struggle to wake up for work? Your internal body clock may be out of sync
It affects up to 15 per cent of teenagers but can be a life-long condition.
Study leader, Professor Leon Lack, said initial results showed that the internal body clocks, of those with the disorder ran slower than average.
'Late sleepers can’t get to sleep until 2am or 3am at the earliest, or in some cases as late as 4am, which makes it very hard for them to get up for their commitments the next day,' he said.
'We’ve been investigating what causes people to be late sleepers and one of the most plausible explanations we’re perusing is that their body clocks run longer than 24 hours.
'Most people have a 24-hour body clock, it’s a natural rhythm that influences sleepiness and core body temperature but for people with delayed sleep phase disorder it takes longer to complete the cycle so they tend to go to bed later and wake up later.'
Circadian rhythms are followed by most living things and follow a daily cycle that are governed by our internal body clocks. They influence sleep and wake cycles, body temperature and the release of hormones.
Exposing the body to bright light early in the morning informs the body clock that it should be awake, say researchers
They can be affected by environmental factors, such as light levels, and so disrupted by flying across time zones and working night shifts.
Professor Lack said wider tests with a larger population would now need to be conducted to confirm the findings.
'If we establish what we’re expecting to find it will reinforce therapies that we know can help, such as bright light therapy to induce alertness in the mornings and melatonin to encourage earlier evening sleepiness,' he said.
'Exposing people to a bright light as early in the day as possible informs the body clock that it should be awake so therefore they fall asleep and wake up earlier on subsequent nights.'
He said it was imperative to find a cause of the condition as it affected so many people.
'It causes young people to be late for school and when they do get to school they’re inattentive until their body clock finally wakes up.
'Adults can also have trouble holding down jobs because they’re always running late for work so it does have a detrimental effect on lives,' he said.
