If you consider yourself a “night owl”, science has your back ― some of us really do have a later chronotype, or natural sleep pattern, than early risers.
An Imperial College London study found that night owls, especially older ones, tended to perform better on cognitive tests when they hit their mental stride. This difference was less severe among younger people.
Nonetheless, most would agree the world is stacked in favour of early risers. But a 2024 study held by Stanford researchers (published in Psychiatry Research) found that it’s not all unfounded bias ― falling asleep past a certain hour seemed to be linked to worse ageing, regardless of chronotype.
How does bedtime affect ageing?
The study looked at the mental health and sleep patterns of 73,888 participants from the UK Biobank.
The researchers wanted to look at how our natural preference for sleep, combined with how we actually slept, affected our mental wellbeing.
There were four groups: night owls who went to bed later (aligned evening types), night owls who slept earlier than they preferred (misaligned evening types), morning larks who got up early (aligned morning types), and early birds who slept later (misaligned morning types).
Misaligned morning types had a higher risk of mental health conditions like depression and anxiety.
But night owls who didn’t get to sleep as late as they wanted to had lower incidences of those conditions.
This surprised the researchers, who had expected better mental health among people who slept when their chronotype wanted them to.
Dr Jamie Zeitzer, lead author of the study, told Stanford: “We found that alignment with your chronotype is not crucial here, and that really it’s being up late that is not good for your mental health.”
The study was run on middle-aged to older adults ― 14% of people over 60 worldwide have mental health issues, which can affect our physical wellness too.
Per the paper: “To age healthily, individuals should start sleeping before 1 am, despite chronobiological preferences.”
Why would that be?
This paper only looked at existing health data, which means it didn’t find a cause ― only an association.
Dr Zeilter himself said his team thought the data “didn’t make any sense” and spent six months trying to disprove it, but couldn’t.
While he has no firm reasons for the link, though, Dr Zeilter theorised that it could be down to the decisions we make when we hit our mental stride.
“If I had to hazard a guess, morning people who are up late are quite cognizant of the fact that their brain isn’t working quite right, so they may put off making bad decisions,” he told Stanford.
“Meanwhile, the evening person who is up late thinks, ‘I’m feeling great. This is a great decision I’m making at 3 o’clock in the morning.’
He also suggested that “there are fewer social constraints late at night because you have fewer people around who are awake.”