P4.40 DIVERSITY OF HAIR GROWTH PARAMETERS: A WORLDWIDE STUDY

G. Loussouarn- C. El Rawadi- G. Genain

L’OREAL Recherche, Clichy, France.

Objective: To evaluate and compare hair growth characteristics of young adult volunteers, native of various countries.

Volunteers / Methods: 1600 healthy volunteers, young male and female adults, aged 18-35, from several countries around the world were involved in the study. Three parameters of hair growth (e.g. hair density, telogen percentage and rate of growth) were recorded, using the phototrichogram technique. Three scalp areas were assessed: vertex, temporal and occipital.

Results: Our data showed a relationship between hair growth rate and the level of curliness. The highest mean values of growth rate (1.3 cm/month) were found in straight hair, particularly in Asian hair, and lowest values in kinky hair (0.8 cm/month for African hair).

On the other hand, no connection was observed between curliness and hair density. The latter parameter seemed rather related to natural shade of hair:  higher hair counts were found in lightest coloured hair.

Regarding the percentage of telogen, the values were close, irrespective of hair features, in the absence of alopecia.

No difference with gender was observed for the 3 measured hair growth parameters in each group. All the populations studied share the feature of heterogeneous hair counts related to scalp location: vertex > occipital >temporal.

Conclusions: Our study evidenced differences in hair growth parameters around the world, notably associated with hair features such as curliness and colour.