title: Diversity in human hair growth, diameter, colour and shape. An in vivo study on young adults from 24 different ethnic groups observed in the five continents.
abstract: Based on previous findings, from a worldwide study, classified the shapes of human hair into 8 major types, from straight to highly curly. This clearly extended the usual classification of hair into African, Asian or Caucasian types. However, determinations of hair growth parameters and hair density were excluded from such studies. To measure and compare the hair growth profiles of young adults without alopecia living in the five continents. 2249 young adults (18-35 years, females and males) without alopecia, originating from 24 various human ethnic groups were included in the study. Total hair density, telogen percentage and growth rate on three different scalp areas were measured, using non-invasive validated techniques. Natural hair colour level, curliness and hair diameter were additionally recorded, when practically possible. Diversity in hair growth parameters among the entire cohort was a key finding, with differences linked to scalp area, gender and geographic origin. Statistical approaches depicted African hair as having lower density and a slower growth rate. Asian hair showed a thicker diameter, with faster growth. Caucasian hair showed a high total hair density. On the one hand, this inter-continental study of hair growth parameters provides initial valuable base-line data on hair in young adults without alopecia, and on the other hand, further extends our knowledge of this unique human appendage, with some mosaic features, observed worldwide.
authors.affiliation: L'OREAL Research and Innovation, 11-13 rue Dora Maar 93400 Saint-Ouen, France.
authors.forename: Geneviève
authors.initials: G
authors.lastname: Loussouarn
authors.affiliation: L'OREAL Research and Innovation, 11-13 rue Dora Maar 93400 Saint-Ouen, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Lozano
authors.affiliation: L'OREAL Research and Innovation, 11-13 rue Dora Maar 93400 Saint-Ouen, France.
authors.forename: Ségolène
authors.initials: S
authors.lastname: Panhard
authors.affiliation: L'OREAL Research and Innovation, 11-13 rue Dora Maar 93400 Saint-Ouen, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Collaudin
authors.affiliation: L'OREAL Research and Innovation, 11-13 rue Dora Maar 93400 Saint-Ouen, France.
authors.forename: Charles
authors.initials: C
authors.lastname: El Rawadi
authors.affiliation: L'OREAL Research and Innovation, 11-13 rue Dora Maar 93400 Saint-Ouen, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Genain
mesh_terms: D000293:Adolescent; D000328:Adult; D000349:Africa / Q000208:ethnology; D000569:Americas / Q000208:ethnology; D001208:Asia / Q000208:ethnology; D004777:Environment; D005006:Ethnicity; D005060:Europe / Q000208:ethnology; D005260:Female; D006197:Hair / Q000033:anatomy & histology* / Q000254:growth & development*; D006200:Hair Color; D006801:Humans; D008297:Male; D044349:Oceania / Q000208:ethnology; D012535:Scalp / Q000502:physiology; D055815:Young Adult
keywords: hair; hair density; hair growth; telogen percentage