Hair test reveals plasticity of human chronotype

The study introduces HairTime, a novel, non-invasive assay that estimates chronotype from a single hair sample, offering a practical alternative to the invasive dim-light melatonin onset (DLMO) method. Evaluated in two studies with over 4,000 samples, HairTime effectively predicts chronotype and reveals its plasticity, particularly in relation to work schedules, which can shift circadian timing. The research highlights the influence of both intrinsic circadian mechanisms and external factors, such as lifestyle, on chronotype. HairTime's ability to facilitate large-scale studies and personalized chronotherapy could improve health outcomes by aligning treatments with individual biological rhythms.