Age, lifestyle and self-perceptions of hair: Is there an association with hair diameter and tensile properties?

OBJECTIVE: To determine the association of age, lifestyle habits and the self-perception of hair condition with the objectively measured physical properties of hair in Caucasian females with brown hair. METHODS: Hair biophysical properties, lifestyle habits data and self-perceptions of hair condition were collected on 110 Caucasian females with brown hair ranging in age from 17 to 78. Hair diameter (cross-sectional area) and tensile properties (elastic modulus, break strength and break extension) were measured at the root end of individual fibres (n = 100/subject) from the crown and frontal regions using objective instrumental methods. Other measures included body mass index (BMI) and Savin female pattern hair loss grades based on judging of standardized front, top and side view head images. Lifestyle habits and practices and self-perceived hair condition were obtained via a standardized self-assessment questionnaire. RESULTS: Hair fibre diameter and break extension decreased significantly with age. Hair fibre elastic modulus and Savin hair loss scores increased significantly with age. No age-related change in hair fibre break stress was observed. A history of smoking or being overweight was significantly associated with having lower hair fibre cross-sectional area but was not associated with any of the measured tensile properties. Subjects who perceived their hair as fine, thinning or weak had significantly lower cross-sectional areas than subjects who did not. Subjects who perceived their hair to be healthy or strong had significantly higher cross-sectional areas than subjects who did not. CONCLUSION: The biophysical properties of hair change significantly with age. A history of smoking or being overweight was significantly associated with having smaller hair cross-sectional area but was not associated with differences in hair tensile properties. The self-perception of having strong or healthy hair seems more associated with having a larger cross-sectional area than any real differences in hair strength.Abstrait.

OBJECTIF: Déterminer l'association entre l'âge, les habitudes de vie et la perception de l'état des cheveux avec les propriétés physiques mesurées de manière objective chez les femmes de race blanche à cheveux bruns. MÉTHODES: Les propriétés biophysiques des cheveux, les données sur les habitudes de vie et la perception de leur état de santé ont été recueillies chez 110 femmes de race blanche aux cheveux bruns âgés de 17 à 78 ans. Le diamètre des cheveux (surface transversale), résistance à la rupture et extension à la rupture) ont été mesurés à la racine des fibres individuelles (n = 100 / sujet) à partir des régions de la couronne et de la partie frontale en utilisant des méthodes instrumentales objectives. Parmi les autres mesures, citons l'indice de masse corporelle (IMC) et les degrés de perte de cheveux selon le modèle féminin de Savin, fondés sur l'évaluation d'images de tête normalisées de face, de dessus et de côté. Les habitudes et pratiques de mode de vie et l'état de poil auto-perçu ont été obtenues à l'aide d'un questionnaire d'autoévaluation standardisé. RÉSULTATS: Le diamètre de la fibre capillaire et l'extension de la rupture ont diminué de manière significative avec l'âge. Le module d'élasticité de la fibre capillaire et les scores de perte de cheveux de Savin augmentaient considérablement avec l'âge. Aucun changement lié au vieillissement du stress lié à la rupture de la fibre capillaire n'a été observé. Des antécédents de tabagisme ou d'embonpoint étaient significativement associés à une section inférieure de la fibre capillaire mais n'étaient associés à aucune des propriétés de traction mesurées. Les sujets qui percevaient leurs cheveux fins, fins ou clairsemés avaient une section transversale significativement plus basse que les autres. Les sujets qui percevaient que leurs cheveux étaient en bonne santé ou forts avaient des zones transversales significativement plus élevées que les sujets qui n'en avaient pas. CONCLUSION: Les propriétés biophysiques des cheveux changent de manière significative avec l'âge. Les antécédents de tabagisme ou d'embonpoint étaient significativement associés à une plus petite section transversale des cheveux mais n'étaient pas associés à des différences de propriétés de tension des cheveux. La perception de soi d'avoir des cheveux forts ou en bonne santé semble plus associée à une plus grande surface transversale que toute différence réelle dans la résistance des cheveux.

Analysis of hair lipids and tensile properties as a function of distance from scalp.

Cuticle cells form the outer covering surrounding and protecting the cortex. The cuticle cells are thin, flat and overlap, and intercellular lipid lamellae are found in the gaps between the cell boundaries. The lipid lamellae are also found within the cortex in the cell boundaries between the long fribrous corticle cells. In addition, the outer surfaces of the cuticle cells are covered by a monolayer of covalently bound fatty acids, a major component of which is 18-methyleicosanoic acid. The fatty acids are thought to be attached through thio-ester linkages. Together these lipids are thought to be major determinants of the physical properties of the hair. The present study tested the hypothesis that both free and covalently bound lipids are progressively lost during normal environmental exposures. This progressive loss within the cuticle layers may, in part, lead to an increased susceptibility of the protein and lipid lamellae in the cortex to degradation. This degradation, in turn, would contribute to a progressive decrease in the tensile properties of the hair. Research grade hair was cut into five segments from the root to the distal end. Lipids from each segment were extracted and analyzed by thin-layer chromatography in conjunction with photodensitometry. The major free polar lipid classes in the hair included ceramides, glucosylceramides and cholesterol sulfate. The concentrations of all of the free polar lipids as well as the covalently bound fatty acids decreased in going from the root to the distal end of the hair. In addition, there was a significant reduction in tensile properties of the hair from the root to distal end. In conclusion, the progressive loss of endogenous free and covalently bound lipids from hair, which are probably related to normal weathering of the hair and grooming practices, may help contribute to a marked decrease in tensile properties to the hair.