People’s grey hairs sometimes naturally regain their original colour, typically when individuals feel less stressed. The finding suggests it may be possible to develop drugs to reverse greying.
Lab mice go grey when stressed and the same thing seems to occur in people. It has long been assumed that once hairs turn grey, they stay that way. But Martin Picard at Columbia University in New York and his colleagues discovered by chance that hair greying sometimes naturally reverses.
The researchers looked at the hair of 14 healthy men and women from different ethnic backgrounds with an average age of 35. They plucked 397 hairs from the participants and studied them under a microscope. They identified hairs that were turning grey by looking for those that were grey at the roots while still coloured at the tips, as new hair grows from the scalp.
To their surprise, the researchers discovered some hairs showed the opposite pattern – they were coloured at the roots and grey at the tips – suggesting they were reverting from grey to their original colour.
Because hair grows at a fixed rate of 1 to 1.3 centimetres per month, the team was able to trace these colour transitions back to specific life events.
The reversals tended to correlate with periods of reduced stress. For example, it occurred in one participant when he went on a two-week holiday and in another after she recovered from the stress of her marriage breakdown.
It is feasible that stress reductions could trigger a reversal of hair greying, says David Fisher at Harvard University. However, it probably only occurs in a few scattered hairs, since we would have noticed if people’s full heads of grey hair changed colour when they felt less stressed, he says. “Most instances of hair greying do not seem to be reversible, but perhaps there is a discreet subset of grey hairs that can do this.”
If we can uncover the biological mechanisms underpinning reverse greying in these few hairs, we may be able to develop drugs that stimulate anti-greying across all hairs, says Fisher. “I think it’s theoretically possible,” he says. We already know that certain cancer drugs seem to stimulate reverse hair greying in a small number of patients, he notes.
One intriguing possibility is that, if grey hair is reversible, ageing in the rest of the body may also be partially reversible, says David Sinclair at Harvard University. It would be interesting to test whether other parts of the body show similar signs of reverse ageing during periods of reduced stress, he says. “It’s definitely worth looking into, now that we have tools to measure biological age accurately,” he says.
newscientist.com, 29 May 2020