For years, the understanding of sleep patterns has largely been divided into two categories: “morning larks” and “night owls.” However, emerging research suggests this categorization is a significant oversimplification. A new study, published in in Nature Communications, identifies five distinct biological subtypes of sleepers, each linked to unique behavioral and health traits. This challenges the conventional wisdom and opens the door to more personalized approaches to sleep, work schedules, and mental health support.
Researchers at McGill University, led by Ph.D. Student Le Zhou, combined brain imaging data with questionnaire responses and medical records from over 27,000 adults in the U.K. Biobank. Their analysis revealed a spectrum of chronotypes – profiles describing when a person feels most alert or sleepy – far more nuanced than previously thought. Similar subtypes were also identified in a separate cohort of over 10,000 U.S. Teenagers, reinforcing the robustness of the findings.
The Five Sleep Subtypes
The study identified two early bird subtypes and three night owl groups. It’s important to note that these aren’t simply defined by bedtime or wake-up time, but rather by a complex interplay of genetic, environmental, and lifestyle factors, as explained by Dr. Danilo Bzdok of McGill University.
Early Bird Subtypes
Subtype 3 represents a “classic” early bird profile, characterized by fewer health problems overall. Individuals in this group tend to avoid smoking, limit alcohol consumption, and engage in fewer risky behaviors. While they may experience higher levels of anxiety, they generally exhibit better emotional regulation.
Subtype 4 is another early-bird chronotype, and tends to include a higher proportion of females. This group is linked to depressive symptoms and a greater likelihood of being prescribed antidepressant medication.
Night Owl Subtypes
Subtype 1, dubbed the “High-Performing Night Owl,” demonstrates faster reaction times and better cognitive performance compared to early birds. However, this subtype is also associated with risky lifestyle behaviors and challenges with emotional regulation.
Subtype 2, the “Vulnerable Owl,” presents a less favorable profile. Individuals in this group are more likely to experience depression, smoke cigarettes, and have a higher risk of cardiovascular problems. They also tend to have lower physical activity levels, reduced white matter integrity in the brain, and are more frequently prescribed antidepressants.
Subtype 5 is a male-dominated night owl group linked to increased consumption of alcohol, cigarettes, and cannabis, as well as elevated risks of cardiovascular disease and prostate issues.
Beyond ‘Early Bird’ vs. ‘Night Owl’
Previous research has linked late chronotypes to poorer health outcomes, but the results have often been inconsistent. This new research suggests that simply categorizing individuals as “night owls” isn’t enough. As Le Zhou points out, “Rather than asking whether night owls are more at risk, the better question may be which night owls are more vulnerable, and why.”
The findings align with a growing body of evidence suggesting that our internal biological clocks, or chronotypes, play a significant role in various aspects of health, including weight management, muscle strength, and aging. Understanding your chronotype could help tailor health recommendations, particularly in areas like weight loss, muscle maintenance, and promoting healthy aging, according to Núria Vilarrasa, MD, professor at the University of Barcelona.
Implications for Personalized Health
The identification of these five sleep subtypes has important implications for personalized health strategies. Rather than advocating for everyone to adopt an “early bird” schedule, the research highlights the importance of aligning lifestyle choices with an individual’s natural sleep patterns. This could involve adjusting work schedules, optimizing exercise routines, and providing targeted mental health support based on a person’s chronotype.
“It may become increasingly evident that our internal sleep phasing system… ties into many more facets of daily life than previously assumed,” the research team concludes. Further research is needed to fully understand the underlying mechanisms driving these chronotype differences and to develop effective interventions tailored to each subtype. However, this study represents a significant step forward in our understanding of the complex relationship between sleep, health, and individual biology.
