Let’s forget, once and for all, the convenient label that divides the world into “larks” and “owls”. Sleep science has just dismantled this simplistic vision and did it with numbers, brains and data in hand. A large international study, which involved over 27 thousand people, shows that our relationship with sleep is much more complex, multifaceted and personal than we have ever been told.
The point is no longer to establish whether we are early risers or night owls, but to understand what kind of early risers or night owls we are, because health, mental well-being, cognitive abilities and even some clinical risks depend on this.
Because dividing people into early risers and night owls is no longer enough
The key concept is that of chronotype, i.e. the biological predisposition – largely genetic – that determines when we tend to sleep, wake up and function better during the day. Until now we have treated it as a simple personal preference, but research shows that there are deep brain mechanisms behind it.
To reach these conclusions, the researchers used two huge archives of biomedical data: one British and one US. They didn’t just ask people “what time do you go to sleep?”, but analyzed three-dimensional brain scans, observing gray matter volume, quality of white matter connections and communication between different brain areas.
What made the difference was the use of artificial intelligence, through an advanced statistical method capable of cross-referencing brain structure and daily behaviour. The result? The discovery of five distinct biological profiles, three linked to the evening and two to the morning.
It’s not just a question of schedule: lifestyle, environment, hormones and mental health come into play. In other words, our sleep tells much more than we imagine.
The five chronotypes
The first profile is that of the high-performance night owl. He is the classic evening type who struggles to get up early but, when active, displays a brilliant mind. He has faster reaction times, excellent reasoning skills and greater efficiency in complex tasks. At the brain level it has particularly developed areas linked to emotions and attention. The downside? Greater difficulty in emotional management and a tendency towards irritability.
The vulnerable night owl is very different. Here, long nights are accompanied by a more fragile picture: this group is more exposed to depression, smoking, hypertension and diabetes. In their brain, a widespread reduction in the integrity of the white matter is observed, as if the “wiring” was less efficient. Not all night owls, therefore, are the same.
Moving on to the morning, we find the healthy early riser, the one who embodies the traditional ideal. He wakes up early, leads a more regular lifestyle, smokes and drinks less and is rarely affected by major health problems. On average, they are more educated and tend to expose themselves less to risks.
Alongside this, a predominantly female morning chronotype emerges. They are mainly women who, despite being early risers, show a greater predisposition to depressive symptoms and menstrual cycle disorders. From a biological point of view, this profile is associated with lower levels of testosterone and a greater presence of SHBG, a protein that regulates sexual hormones.
Finally there is the male-dominated night owl, made up largely of men. It is a profile more prone to risky behavior, with greater consumption of alcohol and cigarettes and a higher probability of developing hypertension and prostate problems. Here testosterone levels are higher, a finding that seems consistent with the more impulsive attitude.
Because this discovery concerns all of us (and not just those who sleep badly)
This variety is not an error of nature. From an evolutionary point of view, having individuals active at different times of the day was a survival strategy: in a primitive community, sleeping all together meant exposing oneself to danger.
Today, however, this discovery has enormous value for the present. It demonstrates why the “one-size-fits-all” approach to health, work and productivity often fails. We don’t all function in the same way, and forcing ourselves into rhythms that don’t belong to us can have a cost.
The research paves the way for more targeted and sustainable interventions: from phototherapy for some more fragile night owls, to tailor-made hormonal or psychological support courses. It is an important step towards more personalized medicine, but also towards a greater understanding of ourselves.
Perhaps the real question, from today on, is no longer “are you an early riser or a night owl?”, but what kind of person are you when you sleep and when you are awake.
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