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      Evaluation of Hair Density and Hair Diameter in the Adult Thai Population Using Quantitative Trichoscopic Analysis

      research-article
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      BioMed Research International
      Hindawi

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          Abstract

          The data of hair density and hair diameter in the Asian population, especially in Thais, are limited. We aimed to evaluate hair density and hair diameter of members of the Thai population at different scalp sites and to determine the effect of sex and aging as well as to compare the results with those in groups of other ethnicities. Healthy Thais whose hair examination findings were normal were evaluated. Two hundred and thirty-nine subjects participated in this study, of whom 79 were male and 160 were female. Hair density and hair diameter were analyzed at four different scalp sites using quantitative trichoscopic analysis. The highest hair density in Thais was observed in the vertex area. Hair densities at four different scalp sites were significantly different from one another; only hair density at the vertex site showed no significant difference from that in the occipital area. In contrast, hair diameter did not show any statistically significant differences for the different sites. We observed decreased mean hair density with increasing age and found statistically significant differences between participants in their 20s and those in their 60s, while hair diameter remained consistent. Comparing our results with a previous study in other ethnicities, the hair densities in Asians are generally lower. In conclusion, hair density in the Thai population varies at different scalp sites. Aging is a factor in declining hair density. Asians have a lower hair density compared to Caucasian and African populations.

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          Most cited references30

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          A scan for genetic determinants of human hair morphology: EDAR is associated with Asian hair thickness.

          Hair morphology is one of the most differentiated traits among human populations. However, genetic backgrounds of hair morphological differences among populations have not been clarified yet. In addition, little is known about the evolutionary forces that have acted on hair morphology. To identify hair morphology-determining genes, the levels of local genetic differentiation in 170 genes that are related to hair morphogenesis were evaluated by using data from the International HapMap project. Among highly differentiated genes, ectodysplasin A receptor (EDAR) harboring an Asian-specific non-synonymous single nucleotide polymorphism (1540T/C, 370Val/Ala) was identified as a strong candidate. Association studies between genotypes and hair morphology revealed that the Asian-specific 1540C allele is associated with increase in hair thickness. Reporter gene assays suggested that 1540T/C affects the activity of the downstream transcription factor NF-kappaB. It was inferred from geographic distribution of 1540T/C and the long-range haplotype test that 1540C arose after the divergence of Asians from Europeans and its frequency has rapidly increased in East Asian populations. These findings lead us to conclude that EDAR is a major genetic determinant of Asian hair thickness and the 1540C allele spread through Asian populations due to recent positive selection.
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            Diagnostic and predictive value of horizontal sections of scalp biopsy specimens in male pattern androgenetic alopecia.

            Vertical sections of small scalp biopsy specimens are often inadequate for the diagnosis of male pattern androgenetic alopecia (MPAA). Quantitative analysis of follicular structures in horizontal sections can provide more information. Our purpose was to establish better diagnostic criteria by comparing horizontal and vertical sections of scalp biopsy specimens from MPAA and normal control subjects and to determine the predictive value of horizontal sections, by relating counts of follicular structures in MPAA to subsequent hair regrowth from topical minoxidil therapy. Paired 4 mm punch biopsy specimens were taken from 22 normal control subjects and 106 patients with MPAA, for horizontal and vertical sectioning. In horizontal sections, hair bulbs, terminal anagen, catagen and telogen hairs, telogen germinal units, and vellus hairs were counted, as were follicular units and stelae. The diagnosis of MPAA was confirmed by finding decreased terminal hairs and increased stelae and vellus hairs. The average horizontal section contained 22 terminal and 13 vellus hairs, a 1.7:1 ratio. Changes compatible with MPAA were found in most vertical and horizontal sections, but horizontal sections were required for follicular counts and showed terminal:vellus hair ratios diagnostic of MPAA in 67% of cases. Of 44 patients treated with topical minoxidil, five with less than 2 follicular structures/mm2 showed no hair regrowth, 32 with 2 to 4 follicular structures/mm2 showed regrowth in 72%, and seven with more than 4 follicular structures/mm2 showed regrowth in 86% of cases. In MPAA with no significant inflammation, regrowth occurred in 77% of cases, versus 55% in cases with significant inflammation. Horizontal sections of scalp biopsy specimens in MPAA provide more diagnostic information than vertical sections and appear to have a predictive value for hair regrowth.
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              Hair density, hair diameter and the prevalence of female pattern hair loss.

              Female pattern hair loss is common but estimates of its prevalence have varied widely. The relationships between the clinical diagnosis of female pattern hair loss and objective measurements of hair density and hair diameter have not previously been evaluated. To determine the prevalence of female pattern hair loss and to relate the clinical findings to hair density and hair diameter. We examined 377 women, aged 18--99 years, who presented to a general dermatology clinic with complaints unrelated to hair growth (the unselected sample). A second group of 47 women referred with typical female pattern hair loss was included in analyses of the relationships between hair density, hair diameter and the clinical diagnosis. Hair density was measured using a photographic method. In each subject the major and minor axis diameters were measured in a random sample of 50 hairs. Six per cent of women aged under 50 years were diagnosed as having female pattern hair loss, increasing to 38% in subjects aged 70 years and over. The mean +/- SEM hair density was 293 +/- 61.3 hairs cm(-2) at age 35 years, falling to 211 +/- 55.1 hairs cm(-2) at age 70 years. Hair density showed a normal distribution in the unselected sample. Most women classified as having female pattern hair loss had hair densities within the lower half of the normal distribution. The perception of hair loss was determined mainly by low hair density (ANOVA P < 0.001), but there was overlap in hair density between women classified as having Ludwig I hair loss and the no hair loss group, which was partly accounted for by differences in mean hair diameter (ANOVA P < 0.001). Low hair density was associated with fewer hairs of all diameters. Hair density in women is distributed as a normal variable, indicating that it is determined as a multifactorial trait. Women with female pattern hair loss have a hair density which falls below the mean but lies within the spectrum of the normal distribution, although other factors, including hair diameter, may affect the subjective impression of hair loss. The hair diameter data suggest that low hair density is not due to progressive diminution in hair follicle size and that follicular miniaturization may occur within the space of a single hair cycle.
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                Author and article information

                Contributors
                Journal
                Biomed Res Int
                Biomed Res Int
                BMRI
                BioMed Research International
                Hindawi
                2314-6133
                2314-6141
                2020
                10 February 2020
                : 2020
                : 2476890
                Affiliations
                Division of Dermatology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
                Author notes

                Academic Editor: Adam Reich

                Author information
                https://orcid.org/0000-0001-9723-0563
                Article
                10.1155/2020/2476890
                7035527
                32104683
                dbb3880d-ce60-469c-a60d-cc1f191654a0
                Copyright © 2020 Kanchana Leerunyakul and Poonkiat Suchonwanit.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 28 August 2019
                : 6 January 2020
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                Research Article

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