The 50/50/50 rule of thumb, which states that “at age 50 years, 50 per cent of the population has at least 50 per cent grey hair”, would appear to be misleading following the French firm’s research into its validity.
Normally when a manufacturer carries out a study and announces the results, it is for some sort of financial gain; a new product to advertise, for example.
However, it would appear this is not the case for L’Oréal, as it hardly urges people to buy its hair dye.
50 rule not true..?
Instead, the hair care maker revisited the study and found instead that the ’50 rule’ may struggle to stand up to its bold claims.
“Calculating the percentage of people showing at least 50 per cent grey hair coverage at age 50 years leads to a global range of 6–23 per cent, according to ethnic/geographical origin and natural hair colour: well below that expressed by the ‘50’ rule of thumb,” says the study’s conclusion.
While numerous papers in the past have reported on the biological mechanisms of human hair pigmentation and greying, epidemiological descriptions of both natural hair colour and the greying process, worldwide, remain scarce; which was the reasoning behind L’Oréal’s research.
To do this, the natural hair colour of 4192 healthy male and female volunteers was assessed using a sensorial expert evaluation through the comparison of each volunteer’s hair with standard samples.
Grey area
Hair colour was studied according to age, gender and ethnic or geographical origin.
“Overall we observed that between 45 and 65 years of age, 74 per cent of people were affected by grey hair with a mean intensity of 27 per cent,” says the study; published online in the British Journal of Dermatology.
“Men harboured significantly more grey hair than women. Both age at onset and rate of greying with age appeared to be clearly linked to ethnic/geographical origin.”
Results showed that subjects of Asian and African descent showed less grey hair than those of caucasian origin, at comparable ages, confirming previously reported data.