Did you know that hair follicle cells have “clock genes” that regulate different processes, including hair growth? A study published in 2010 by the Proceedings of the National Academy of Sciences of the United States of America (PNAS) discovered these genes, previously thought to be restricted to specific areas of the body. The study also showed that the circadian rhythm is crucial in coordinating the hair growth cycle. Meanwhile, the 2023 study in the International Journal of Molecular Sciences found that these “clock genes” in hair follicles are synchronized with the central circadian clock located in the brain.
Circadian clock genes were found to play an active role in regulating hair follicle cycling in a 2009 study published in PLOS Genetics. These genes control the growth and rest phases of hair follicles, ultimately impacting hair thickness and quality. Understanding the correlation between hair growth and the circadian rhythm has practical implications for evaluating your sleep quality through the strands of your hair.