Quantitative mapping of human hair greying and reversal in relation to life stress.

BACKGROUND: Hair greying is a hallmark of aging generally believed to be irreversible and linked to psychological stress. METHODS: Here, we develop an approach to profile hair pigmentation patterns (HPPs) along individual human hair shafts, producing quantifiable physical timescales of rapid greying transitions. RESULTS: Using this method, we show white/grey hairs that naturally regain pigmentation across sex, ethnicities, ages, and body regions, thereby quantitatively defining the reversibility of greying in humans. Molecularly, grey hairs upregulate proteins related to energy metabolism, mitochondria, and antioxidant defenses. Combining HPP profiling and proteomics on single hairs, we also report hair greying and reversal that can occur in parallel with psychological stressors. To generalize these observations, we develop a computational simulation, which suggests a threshold-based mechanism for the temporary reversibility of greying. CONCLUSIONS: Overall, this new method to quantitatively map recent life history in HPPs provides an opportunity to longitudinally examine the influence of recent life exposures on human biology. FUNDING: This work was supported by the Wharton Fund and NIH grants GM119793, MH119336, and AG066828 (MP).