Molecular Gene Analysis of Hair Follicle Roots Provides New Non Invasive Method for Determining Individual Biological Rhythms

Charité researchers develop a non invasive hair root test to map circadian rhythms, enabling personalized medicine and better timing for medical treatments.

By: AXL Media

Published: Apr 1, 2026, 11:54 AM EDT

Source: Information for this report was sourced from Charité - Universitätsmedizin Berlin

The Biological Significance of the Internal Clock

The human body operates on a sophisticated 24 hour rhythm that governs far more than just sleep cycles and wakefulness. This internal clock regulates critical functions including metabolism, hormonal balance, and the responsiveness of the immune system to external interventions. Professor Achim Kramer, who leads the Division of Chronobiology at Charité, explains that the timing of medical treatments, such as cancer immunotherapies, can significantly alter their effectiveness. Because organs and immune cells follow distinct rhythmic patterns that vary from person to person, a universal approach to medicine often misses the window of peak biological receptivity. The transition toward circadian medicine seeks to bridge this gap by aligning clinical therapies with the unique temporal needs of each patient.

Follicle Based Gene Mapping vs Melatonin Testing

Until recently, determining a person's precise biological rhythm required the labor intensive process of measuring melatonin levels in saliva under strictly controlled dim light conditions. This traditional method, while accurate, is often impractical for large scale clinical use due to its requirement for multi hour laboratory monitoring. The new approach developed at Charité simplifies this process by focusing on the roots of a single hair sample. Within these follicles, scientists measure the expression levels of 17 specific genes that are either part of the molecular clock or directly regulated by it. By applying machine learning to these genetic patterns, researchers can calculate a person’s current position in their daily cycle with a high degree of precision from just one sample.

Demographic Variations in Circadian Rhythms

In a massive study involving approximately 4,000 participants, the hair analysis test confirmed several long held theories about how biological clocks change over time. The data revealed that age plays a significant role in chronotype, with individuals in their mid 20s typically becoming tired an hour later than those over the age of 50. Furthermore, the study highlighted subtle but consistent differences between genders, noting that the internal clocks of women signal the start of the night slightly earlier than those of men. While the six minute average difference found in the study was smaller than what previous questionnaires su...