Scientists Discover Five Distinct Sleep Types Beyond Night Owls and Early Birds

Beyond the Binary: Sleep Is More Complex Than We Thought

The age-old division between morning larks and night owls has been shattered by groundbreaking research that reveals five distinct sleep types, each carrying unique health risks and cognitive benefits. According to new research, there are five unique types of sleepers out there, and which kind you are is tied to your health and lifestyle, with researchers identifying five subtypes of the "early bird" and "night owl" sleep–wake patterns, each associated with different patterns of behavior and health.

Using AI, researchers combined brain imaging with questionnaires and medical records from more than 27,000 adults in the U.K. Biobank. The study, published in Nature Communications, challenges decades of sleep research that treated chronotypes as simple categories. "These subtypes are not defined only by bedtime or wake-up time. They reflect a complex interaction of genetic, environmental and lifestyle factors," said senior author Danilo Bzdok, Associate Professor in McGill's Department of Biomedical Engineering.

Their analysis revealed three types of night owls and two types of early birds. Rather than ranking sleep types as superior or inferior, the findings show how health risks and cognitive strengths are distributed differently across each profile.

The Five Sleep Subtypes Revealed

The research identified two dramatically different types of early risers. The Healthy Early Bird represents the classic standard of positive morning lovers - these individuals get up early, smoke less, drink less, and have almost no major health issues reported in their medical records. They are often more educated and take fewer risks. In stark contrast, the Female-Biased Morning Type is predominantly seen in women who, while they are early risers, are also more prone to depressive symptoms and menstruation disorders, biologically linked to lower testosterone and higher sex hormone-binding globulin.

Night owls show even greater complexity across three distinct subtypes. The High-Performing Night Owl represents the "classic" evening type, late waker, but with a cognitive edge. While they often struggle with emotional regulation and often report feeling "fed up" or irritable, they are cognitively sharp, showing faster reaction times and better performance in puzzle-solving tasks.

The Vulnerable Owl reveals a darker side of late nights, strongly linked to depression, smoking, and cardiovascular risks like high blood pressure and diabetes, with their defining feature being a widespread reduction in the integrity of their brain's white matter "wiring". The Male-Biased Night Owl represents a distinctly male-heavy evening group who are risk-takers consuming more alcohol and cigarettes and face higher risks of prostate issues and hypertension, with their profile marked by higher testosterone levels.

Brain Differences Drive Sleep Patterns

Using data from over 700 participants, researchers found that different sleep patterns—ranging from poor quality to resilience and short duration—each showed unique neural connectivity patterns. For instance, those with poor sleep displayed stronger links between attention and sensorimotor networks, correlating with anxiety and depression. High-performing night owls show increased gray matter in the limbic system and stronger wiring in attention networks.

To validate these findings, the team looked at 10,550 US children from the ABCD Study and found the same biological patterns in youth, but they can change as people age. This suggests that sleep subtypes aren't fixed destiny but evolving biological patterns that shift throughout life.

Personalized Sleep Medicine on the Horizon

A more nuanced understanding of sleep profiles can help explain why the same sleep schedule can affect people differently, shifting research and sleep support away from one-size-fits-all approaches. This research suggests that sleep problems come in many forms, and therefore improving them likely won't have a one-size-fits-all solution. Better sleep may require more personalized approaches taking into account not just how long you sleep but how your emotional state, daily routines and physical health affect one another.

"Understanding this biological diversity could eventually help inform more personalized approaches to sleep, work schedules, and mental health support," said Le Zhou, a neuroscience grad student from McGill University. As sleep medicine evolves beyond simple duration metrics, these discoveries could revolutionize how we diagnose sleep disorders, design workplace schedules, and develop targeted interventions that match individual biological profiles rather than applying universal solutions to diverse sleep needs.