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<\/p>\nNew research led by McGill University scientists suggests human sleep patterns (chronotypes) fall along a broader biological spectrum \u2014 with each subtype tied to unique health and behavioral traits \u2014 challenging the simple \u2018early bird\/night owl\u2019 divide.<\/p>\n
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Zhou et al. identify a total of five distinct biological subtypes, each associated with different patterns of behavior and health. Image credit: Wok & Apix.<\/p>\n
A chronotype is based on the parts of a 24-hour period when a person naturally feels most alert or ready to sleep.<\/p>\n
Previous research has linked late chronotypes to worse health outcomes, but results have often been inconsistent.<\/p>\n
\u201cRather than asking whether night owls are more at risk, the better question may be which night owls are more vulnerable, and why,\u201d said Le Zhou, a Ph.D. student at McGill University.<\/p>\n
Using AI, Zhou and colleagues combined brain imaging with questionnaires and medical records from more than 27,000 adults in the U.K. Biobank.<\/p>\n
Their analysis revealed three types of night owls and two types of early birds.<\/p>\n
One group of early birds had the fewest health problems overall, while the other was closely tied to depression.<\/p>\n
As for night owls, one performed better than other groups in cognitive tests but had more emotional-regulation challenges.<\/p>\n
Another group showed a tendency toward risk-taking behaviors and cardiovascular problems, while a third was more likely to have depression, smoke and face higher risks of heart disease.<\/p>\n
\u201cThese subtypes are not defined only by bedtime or wake-up time,\u201d said McGill University\u2019s Dr. Danilo Bzdok.<\/p>\n
\u201cThey reflect a complex interaction of genetic, environmental and lifestyle factors.\u201d<\/p>\n
Rather than ranking sleep types as better or worse, the researchers highlight how risks and strengths are distributed differently across the five profiles.<\/p>\n
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.<\/p>\n
\u201cIn today\u2019s digital and post-pandemic era, sleep patterns are more diverse than ever,\u201d Zhou said.<\/p>\n
\u201cUnderstanding this biological diversity could eventually help inform more personalized approaches to sleep, work schedules and mental health support.\u201d<\/p>\n