Researchers at Charité – Universitätsmedizin Berlin have developed a new test that uses a single hair sample to determine a person's internal clock rhythm, known as their chronotype. This innovative approach could pave the way for advancements in circadian medicine, which aligns treatment with the body's natural functioning throughout the day.
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In a study involving approximately 4,000 participants, the team found that biological timing varies slightly between genders and is significantly influenced by lifestyle factors. The findings were published in the Proceedings of the National Academy of Sciences.
The internal clock regulates various bodily functions beyond sleep, including hormone release, digestion, and drug metabolism. Prof. Achim Kramer, head of the Division of Chronobiology at Charité, noted that the timing of certain treatments, such as cancer immunotherapies, can greatly affect their efficacy because bodily systems, including the immune system, follow a 24-hour rhythm that can vary by individual.
Traditionally, measuring an individual's biological rhythm involved tracking melatonin levels in saliva under laboratory conditions, which is complex and not practical for widespread use. The new method analyzes cells from hair follicles, measuring the activity of 17 genes associated with the body's internal clock. Using machine learning, the researchers can estimate an individual's position in their daily rhythm from a single hair sample.
The study confirmed previous survey findings about age and gender differences in circadian rhythm. Individuals in their mid-20s typically go to sleep about an hour later than those over 50, while women showed slightly earlier internal timing than men, with a difference of about six minutes.
Unexpectedly, lifestyle also showed a strong influence; those in employment had internal clocks running about half an hour earlier than unemployed individuals.
The research team aims to standardize the hair analysis test for routine clinical applications, potentially assisting in sleep counseling and diagnosing sleep disorders. Future applications could include optimizing treatments based on patients' circadian rhythms to improve their effectiveness and minimize side effects.
The study was supported by BodyClock Technologies GmbH, a company established to market the new test, and part of the research was conducted within the Collaborative Research Center “Foundations of Circadian Medicine,” funded by the German Research Foundation.