Greying of the human hair. A worldwide survey, re-visiting the 50 rule of thumb.
British Journal of Dermatology, 06/26/2012
Panhard S et al. – Calculating the percentage of people showing at least a 50% grey hair coverage at age 50 age, leads to a global range of 6% to 23%, according to ethnic/geographic origins and the natural hair colour, appearing well below that expressed in the “50” rule of thumb.