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Normal head‐hair length is correlated with its diameter
Author(s) -
Nissimov J.
Publication year - 2004
Publication title -
clinical and experimental dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 78
eISSN - 1365-2230
pISSN - 0307-6938
DOI - 10.1111/j.1365-2230.2004.01629.x
Subject(s) - miniaturization , anatomy , medicine , materials science , nanotechnology
Summary Shed head‐hair fibres of young (16–20‐year‐old), nonalopecic women ( n = 25), exhibiting both exogen clubs and anagen tips (EA) were studied. Such fibres are shown, for the first time, to comprise ≈ 44% of shed hair and to form a uni‐modal, positively skewed distribution with a mean length of 16.7 ± 4.9 cm, which is also correlated with the length of the haircut. As individual fibres exit the skin in early anagen VI, their major‐axis diameters increase rapidly to maxima at about 25% of their total potential length and subsequently decrease to their exogen clubs, at a rate of 1.31% per cm ( n = 28). EA diameters are further correlated with their lengths. Maximal and proximal diameters increase by 1.40% per cm and 1.02% per cm increments in fibre lengths, respectively ( P < 0.0001 each; n = 14), these changes being also different from each other ( P < 0.001). Besides identifying and characterizing a new class of normal hair (EA) which will probably feature prominently in future hair research, this study reveals several other important aspects of hair growth: (i) the classically described concept of hair miniaturization in androgenetic alopecia (AGA) is excessively broad and should therefore be revised; (ii) female AGA need not necessarily require a mechanism for rapid miniaturization as recently proposed; and (iii) the putative large variability of normal hair diameters is significantly overestimated, which further opens the field of hair diameter evaluation as a biological indicator of disease and physiological function.