The study found 18-year-olds should sleep at 12.30am and wake up at 8.30am. [Photo: huffingtonpost.com]
Teenagers are notorious for being impossible to drag from their beds in the morning.
But they actually do need a lie-in of up to 90 minutes longer in the morning, according to a scientific study.
US scientists have found teenagers have a later body clock, which makes them night owls so that they go to bed late and wake up early.
The optimum bedtime for 17 and 18-year-olds is 12.30am, while they should wake up at 8.30am. That is compared to 60-year-olds, who are larks and typically go to bed at 11pm to rise an hour and a half earlier than teenagers at 7am.
The findings are based on data from almost 54,000 people from 2003 to 2014.
Teenagers have a later body clock, which makes them night owls, so that they go to bed late and wake up early, scientists have found.
It is unknown why teenagers' sleeping patterns make them sleep later, only to start getting up earlier around the age of 19.
But the study states that blue light from smartphones and tablets may be affecting human circadian rhythms, while some experts say their habit of staying up late might also be changing their body clocks.
Men also sleep later than women up until the age of 40, perhaps because women's lives are changing their sleeping patterns through less exposure to natural light as they take on the bulk of housework and childcare.
The researchers, whose study on sleeping patterns, or chronotypes, is published in the journal PLOS One, said: "What chronotype you are, is influenced by age and gender - on average, older people are earlier chronotypes than younger people and women are earlier chronotypes than men during the first half of their lives."