Is starting work at 9am really bad for you? For teenagers and many young adults, the science points fairly clearly to yes: their body clocks run later than the school or office day, so early starts cut into sleep they cannot easily make up. For most adults over about 25 the picture is more mixed. Some people are natural early birds, many sit in the middle, and a minority are night owls who genuinely struggle before mid-morning. The idea that every adult under 55 is out of step with nine-to-five hours, and that early work amounts to torture, is a memorable claim from one researcher rather than settled science.
Here is where that claim came from, how the body clock actually works, what the school trials found, and what you can do if mornings feel impossible.
Where the "work before 10am is torture" claim came from
The idea comes from Paul Kelley, a former head teacher who became a sleep and memory researcher, working at the time with Oxford University's sleep and circadian neuroscience group. Speaking at the British Science Festival in September 2015, he argued that standard working and school hours ignore human biology and leave workers and pupils chronically short of sleep. Newspapers, including Canada's National Post, ran the story under headlines about early starts being a form of torture.
His central point was that the cost is not only tiredness. Kelley put it bluntly:
"Staff are usually sleep deprived. We've got a sleep-deprived society."
Paul Kelley, as reported in 2015
He suggested ideal start times rising with age: around 8:30am for ten-year-olds, 10am for sixteen-year-olds and 11am for university students. Those numbers are his proposals, built on circadian research, not results from large trials. Feeling dread at the alarm, a theme of our piece on hitting the snooze button, is common, but it is not proof that a particular hour is harmful for everyone.
How your body clock works
Nearly every cell runs on a roughly 24-hour cycle known as a circadian rhythm. A small cluster of neurons in the brain's hypothalamus, the suprachiasmatic nucleus, keeps those cycles in time, using light reaching the eyes as its main signal. In the evening, as light fades, the body releases melatonin and core temperature drops, which makes sleep easier. In the morning the process reverses.
Not everyone's clock is set to the same hour. Researchers call each person's natural timing their chronotype. A survey of more than 55,000 people led by chronobiologist Till Roenneberg found that chronotypes form a bell curve: a few extreme larks, a few extreme owls, and most people somewhere in between.
Chronotype also shifts with age. Young children tend to wake early, adolescents drift later, timing is latest around the end of the teens and early twenties, and many people become earlier again in later life. When work or school forces someone to wake well before their body is ready, they build up a weekly sleep debt and then sleep in at weekends. Roenneberg coined the term "social jetlag" for that weekly swing.
Your organs follow the same master clock but with their own timing, which is why shifting sleep by a few hours can upset digestion, appetite and mood, not only alertness.
What school start-time research shows
Kelley tested his ideas while he was head teacher of Monkseaton High School in North Tyneside, in north-east England. The school moved its start from 8:50am to 10am, and Kelley reported better attendance and a rise in top exam grades; when the school later returned to the earlier start, performance reportedly fell. A single school is not a controlled trial, so those figures are best read as encouraging rather than conclusive.
He kept working on the question. In a paper published in Frontiers in Human Neuroscience on 8 December 2017, Kelley, then at The Open University, and colleagues from Harvard and the University of Nevada, Reno reported that absence due to illness among pupils aged 13 to 16 fell by more than half after a switch from 8:30am to 10am.
Larger studies elsewhere point in the same direction:
- In 2014 the American Academy of Pediatrics recommended that middle and high schools start no earlier than 8:30am, calling teenage sleep loss a public health problem.
- California became the first US state to legislate on this. From 2022 its high schools may not start before 8:30am and its middle schools not before 8am.
- One study found the share of pupils getting eight hours of sleep rose from about 16 percent to about 55 percent after a 30-minute delay.
- In Wake County, North Carolina, a one-hour later start for middle schools was linked to small gains in maths and reading, with the biggest benefit for lower-scoring pupils.
Later starts have also been associated with fewer late arrivals, less depression and fewer crashes involving teenage drivers.
What about adults at work?
The adult evidence is thinner and messier. The school findings cannot be copied straight across, because adults are spread more evenly across chronotypes and many larks would find a 10am start pointless or even worse. Kelley's claim that adults under 55 are completely out of sync with nine-to-five hours goes further than most sleep scientists would.
What is well supported is that a mismatch between someone's body clock and their working hours carries a cost. Night and rotating shift work is linked to poorer sleep and a higher risk of several health problems, and chronic short sleep affects mood, concentration, reaction times and metabolism. Our article on sleep deprivation covers those effects in more detail. A night owl forced into early starts for years is effectively living with a mild version of that mismatch.
That is why many employers now offer flexible start times. Letting staff choose a window, for example arriving between 7am and 10am, lets larks and owls each work when they are sharpest without changing the hours of the whole organisation.
Common myths about mornings and sleep
"Early risers are more disciplined." Chronotype is partly inherited and changes with age. Being an owl is not laziness, and an owl who sleeps 7 to 9 hours on a later schedule is not doing anything wrong.
"Everyone should start at 10am." No single hour suits a whole population. The best evidence for later starts is for teenagers.
"Your body clock cannot be changed." It can be nudged. Bright morning light shifts most people earlier, while bright light and screens late at night push them later. The shift is limited, though, and a strong owl will rarely become a natural lark.
"You can catch up at the weekend." A long lie-in helps a little, but a big weekend swing is the social jetlag that keeps Monday mornings hard.
Practical ways to make early starts easier
- Keep your wake-up time steady, including weekends, within about an hour.
- Get outdoor light soon after waking, even on a cloudy day; it is far brighter than indoor lighting.
- Dim lights and screens in the last hour before bed, and keep caffeine to the morning.
- Work out how much sleep you need on holiday, when you wake without an alarm, and count back from your alarm to set a bedtime.
- If your job allows it, ask about flexible hours and schedule demanding tasks for your sharpest time of day.
- If you are sleepy every day despite enough time in bed, snore heavily or struggle to sleep at all, talk to a doctor. Sleep disorders are common and treatable.
The core lesson from this research is less about a magic hour and more about fit. When daily schedules respect how body clocks change with age and differ between people, sleep, health and performance all tend to improve.
Sources: The Open University: Teenagers' health is better with later school start (December 2017); Wikipedia: Chronotype; Wikipedia: Start school later movement. Paul Kelley's 2015 comments were originally reported by the National Post.
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