If getting into work this morning was a struggle, you're not alone: an expert has said being forced to start work before 9am is a form of "torture".
Oxford University's Dr Paul Kelley told the British Science Festival that the majority of office workers are sleep-deprived because the body's 24-hour circadian rhythm is set.
"You cannot learn to get up at a certain time. Your body will be attuned to sunlight," he said.
"[Getting up early] is hugely damaging on the body's systems because you are affecting physical emotional and performance systems in the body."
He added that the way our bodies tune themselves to the ebb and flow of time changes as we become older. While children wake and go to sleep earlier, teenagers and those in their early 20s start and end their days as much as three hours later.
"You don't get back to the [earlier] starting point until 55," he said.
Because of that, he called on bosses to change their workers' hours, saying sleep-deprivation was an "international issue".
"Staff should start at 10am... Staff are usually sleep-deprived. We've got a sleep-deprived society."