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This article is presented as part of CBC Health's Second Opinion, a weekly analysis of health and medical science news delivered to subscribers every Saturday morning.
The traditional dichotomy of "early birds" versus "night owls" as the sole descriptors of human sleep patterns may be overly simplistic, according to new research. While previous studies have often linked later chronotypes—an individual's natural inclination for sleep, wakefulness, and peak performance—to poorer health outcomes, the consistency of these findings has been questioned. Recent advancements in sleep science are now offering a more nuanced perspective on how these biological rhythms influence our well-being and behavior.
A groundbreaking Canadian-led study, involving over 27,000 U.K. adults, and published in Nature Communications, is providing critical insights. This extensive research aims to identify individuals who could most benefit from prioritizing specific lifestyle factors like sleep, physical activity, or social engagement, and at what times. The methodology integrated comprehensive brain imaging with computer science, alongside questionnaires, cognitive assessments, and medical chart reviews, painting a detailed picture of diverse chronotypes.
Unpacking Diverse Sleep Chronotypes and Their Health Links
The prevailing notion that night owls inherently exhibit less healthy lifestyles compared to early birds is a significant oversimplification, states Le Zhou, the study's lead author and a PhD student in neuroscience at McGill University. "People always think the night owls tend to have bad health patterns and the early bird people tend to have healthier lifestyles," he observed. "But our study found, actually, the short answer is not." This research moved beyond merely correlating late sleepers with health risks, instead seeking to uncover specific vulnerabilities and strengths within various chronotype groups.
The investigation identified five distinct subtypes across both self-identified night owls and early birds, each linked to unique behavioral and health patterns. Among those identifying as night owls, three subgroups emerged: one group demonstrated superior performance in cognitive tests but struggled with emotional regulation, often displaying impulsive behaviors or addictive tendencies such as smoking and substance use. Another night owl group lacked enhanced cognitive abilities and engaged in less physical activity due to their schedules, showing elevated cardiovascular risks and depression levels. The third comprised energetic individuals, predominantly male, who were highly active and social, often consuming more alcohol and exhibiting higher average testosterone levels.
For early birds, two primary subtypes were discovered. One group maintained stable lifestyles with minimal risk-taking behaviors, rarely smoked or drank, and participated in social clubs, experiencing the fewest overall health problems. The second early bird group, however, showed a stronger correlation with depression and typically presented with more characteristic female hormone patterns, including lower testosterone. Based on these findings, Zhou suggested that night owls might benefit more from increasing physical activity and adopting healthier coping mechanisms for anxiety, rather than trying to alter their natural sleep timing. High-performing night owls, in particular, could manage impulsivity and substance use by aligning with their inherent rhythms, while early risers facing challenges might improve their well-being by enhancing social support.
Expert Perspectives and Practical Sleep Optimization
While the study offers profound insights, Rébecca Robillard, a professor at the University of Ottawa not involved in the research, pointed out a methodological limitation: the reliance on self-identified chronotypes via a simple questionnaire. She noted that incorporating multiple biological measures, such as hormonal or temperature fluctuations, would lend greater robustness to the findings, an avenue she anticipates future research will explore. Conversely, Dr. Michael Mak of the Centre for Addiction and Mental Health in Toronto, also independent of the study, highlighted a key strength: the validation of the findings against another database of younger U.S. individuals, bolstering confidence in the conclusions drawn from such a large-scale analysis.
For individuals seeking to understand their own sleep patterns, Jessica Chalekas, an expert in the sociocultural anthropology of sleep at Brunel University in London, England, suggests a straightforward approach. She advises dedicating a week or two to self-observation, paying close attention to when one naturally feels most functional. Robillard, who directs a clinical sleep research unit, emphasizes adapting daily routines to allow one's chronotype to flourish. This could involve strategic light exposure for later risers to gently shift their internal circadian rhythm earlier. She recommends simple actions like taking a morning coffee break outdoors, even on cloudy days, as sunlight acts as a powerful ally.
Embracing Your Circadian Rhythm for Enhanced Wellness
The consistency of one's sleep schedule also plays a crucial role, according to Robillard. Fluctuating between early weekday wake-ups and late weekend lie-ins sends conflicting signals to the body's internal clock, hindering its ability to maintain a stable rhythm. However, Dr. Mak, a sleep medicine specialist, cautions about the limitations of attempting to drastically alter one's inherent chronotype, noting that such changes are unlikely to be permanent or fully mitigate associated health risks.
Dr. Maha Alattar, an associate professor of neurology at Virginia Commonwealth University and a sleep specialist, actively works to dispel societal misconceptions about late chronotypes. "One of the things that I do with a lot of those patients, when I figure out that's what they have, is to reassure them that you're not lazy," Alattar explained. "You just have this circadian rhythm that's not in line with the world schedule. And there's nothing wrong with you, but it is your obligation to make sure that you have good habits in the evening and in the morning." She also highlights how chronotypes can become dysfunctional in certain populations, such as individuals in nursing homes or those with dementia, where the brain's ability to generate circadian rhythms diminishes. Ultimately, respecting one's biological need for sleep and wakefulness is paramount, as Alattar concludes: "A good night's sleep is an investment in your health."
