Grey hair is one of the first associations we tend to make with the aging process. This change in physical appearance is caused by the loss of melanin. Hairs grow from a living hair follicle into a hardened hair shaft (HS). Melanosomes (melanin-containing organelles), produced by melanocytes, are present within the HS and lost during hair greying. White hairs appear to show a >98% absence of melanin. A recent study published in eLife (‘Quantitative mapping of human hair greying and reversal in relation to life stress’) has provided evidence for the association between psychological stress and hair greying as well as the reversibility of this process.
Evaluating the recent study in this area
In this study, local adverts, together with a snowball recruitment strategy, were used to recruit participants who identified themselves as having ‘two-coloured hairs’ or ‘some grey hairs’. There was an equal distribution of males and females totalling 14 participants with a mean age of 35 ± 13 (SD, range: 9-65). This age range was used to represent the beginning of the aging process as this is when events such as repigmentation are most likely to occur.
The hairs were photographed for visualisation and high-resolution hair pigmentation patterns (HPPs) were generated. Electron microscopy was used to analyse the hair of two specific individuals (an African American male and a Caucasian male). Quantification of cortex and melanin granule intensity from the electron micrograph then allowed for computation of melanin granule density per hair region. Mitochondria play a crucial role in the energy consumption and metabolism of this active hair greying process. Real-time quantitative polymerase chain reaction could determine mitochondrial DNA (mtDNA) copy number and thus quantify HS mtDNA from these two individuals. Statistical tests were used to analyse the data. The use of mass spectrometry proteomics within the study of all 14 individuals is of particular interest given AgeCurve’s use of this platform to track the aging journey.
Hair greying is linked to stress
The importance of maintaining a healthy psychological wellbeing is continually being promoted. This is because several links between stress and biological age have been made based on different measurements including telomere length. The association between these two key factors has been confirmed in this study on hair greying. Mapping of HPPs in this study allowed for quantification of hair colour changes. Identifying hairs that were only partially grey was the first step towards identifying the aging period for these individual hair strands. The average growth rate of human hair is currently set at approximately one centimetre per month. This value was used in calculations to determine the times when the hair colour change happened. The timing of colour change events was then aligned with stressful events in the participant’s life. Hair pigmentation was found to change in response to stress as stress above a certain ‘threshold’ could induce depigmentation.
Hair greying can be reversed
The exact age of onset of hair greying differs greatly across individuals. Adults who are beginning to experience hair greying often report it to be a patchwork process. This is because grey hairs are unevenly distributed throughout the body during the initial stages of hair greying. Many of the ‘grey hairs’ analysed in this study were found to actually be coloured at the base and only grey at the tip. This demonstrated that identifying the onset of depigmentation is particularly important given the potential for reversibility. This is because there were many occasions where ‘white hairs’ naturally reverted back to their dark pigmented state. Grey hair reversal coincided with relaxation events in a participant’s life such as going on holiday. This emphasises how greying is linked to changes in mitochondrial proteins and metabolic pathways that have the potential to be altered.
Limitations of this study
This study has brought together some previous findings from individual case studies. Despite the robustness of the data provided, it is worth evaluating several limitations of this study. This includes the small number of participants involved as only 14 participants were identified within a 2.5 year recruitment period. Reversibility was also limited to isolated hair follicles. Further research may therefore be required to understand whether reversibility is a widespread phenomenon across more people representing a larger spread of age groups.
What does this mean for the future?
Overall, our hair has the potential to hold information about our past life events. This is analogous to certain events in nature such as tree rings holding information about past decades. Mapping HPPs opens up many more possibilities for future tracking of the aging process. This may also be used across the field for situations such as assessing the effectiveness of aging treatments.
The fact that a stressful event can initiate the greying process confirms the importance of psychological health in decelerating the aging process. Environmental factors also affect the hair follicle pigmentary unit (HFPU) as shown by cases of hair depigmentation induced by drugs or mineral deficiencies.
Physical appearance and the importance of ‘looking young’ has become increasingly valued in modern society. Most adults currently rely on hair colorants to cover up grey hairs. Research in this area opens up the potential for future greying reversal interventions that potentially exploit the natural repigmentation process. There is also hope for the future development of drugs to prevent hair greying.
The overall malleability of this process highlights the importance of our active role in decelerating our own biological aging journey.
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*Disclaimer: This information is for educational purposes only