A healthcare expert has warned that making peopleunder the age of 55 years to start their workday at 9am is equivalent to torture for employees.

One of the UK's leading sleep experts, Dr Paul Kelley warned that making people work from nine-to-five leaves their bodies exhausted and stressed due to sleep deprivation. The expert from the Oxford University has said that it might pose a threat to performance until the age of 55 when humans tend to need less sleep.

Dr Kelley, said, “We cannot change our 24-hour rhythms. You cannot learn to get up at a certain time. Your body will be attuned to sunlight and you're not conscious of it because it reports to hypothalamus, not sight.This applies in the bigger picture to prisons and hospitals. They wake up people and give people food they don't want. You're more biddable because you're totally out of it. Sleep deprivation is a torture.”

Dr Kelley, who works as a honorary clinical research fellow at Oxford University's Sleep and Circadian Neuroscience Institute, said that the authorities should consider changing work and school starting times to adapt to the natural human body clock. While speaking at the British Science Festival in Bradford, he said that the workday should start at 10am.