Abstract
Introduction
Documenting normal hair values through trichoscopy can provide a useful baseline when evaluating and treating hair loss in different populations. The aim of our study was to document normal values for measurable parameters of hair in adult Egyptian females.
Methods
This cross-sectional study involved 90 Egyptian females (age range 18–48 years), with no symptoms or signs of hair or scalp disease. Trichoscopy was performed in different scalp areas using FotoFinder Medicam 1000 videodermoscopy. Trichoscopy images were subjected to statistical processing using TrichoLAB system.
Results
The frontal area demonstrated the highest number of hairs (190 ± 29/cm<sup>2</sup>), greatest average hair shaft thickness (63 ± 8 μm), greatest percentage of thick hairs (71% ± 12), highest mean cumulative hair thickness (12 ± 2 mm/cm<sup>2</sup>), and highest mean number of follicular units (82 ± 8/cm<sup>2</sup>). The temporal area showed the highest percentage of thin hairs (9% ± 5) and single-hair pilosebaceous units (23% ± 7), lowest mean number of hairs (154 ± 25/cm<sup>2</sup>), least average hair shaft thickness (60 ± 9 μm), least mean cumulative hair thickness (9 ± 2 mm/cm<sup>2</sup>), and least mean number of follicular units (70 ± 8/cm<sup>2</sup>). The occipital area showed the greatest percentage of triple-hair follicles (43% ± 12). Based on trichoscopy, the norms for hair parameters were calculated.
Conclusion
Normal hair parameters in adult Egyptian females differ from those documented from other ethnicities. Evaluating and treating hair loss in clinical practice should be done in reference to documented normal values, which can be set through trichoscopy.
Keywords: Trichoscopy, Videodermoscopy, Measurable parameters, Egyptian females
Introduction
Trichoscopy (hair and scalp videodermoscopy) is a simple and noninvasive diagnostic tool in dermatology that allows digital surveillance and monitoring of patients [1]. On the other hand, the use of trichoscopy can result in lower diagnostic accuracy if the physician does not recognize or correctly interpret the significance of findings [2].
Establishment of normal values of measurable hair parameters to provide a framework for future reference has been previously performed. A study by Rakowska [3] was conducted in Poland in 2009 to establish norms of measurable parameters for a population of adult white females using trichoscopy. In 2019, Buch and Criton [4] documented the various trichoscopic findings of different age groups of a total of 750 healthy children under 17 years of Malayalam-speaking ethnicity. Both of the above studies proposed a summary of trichoscopic patterns of normal hair and scalp in an attempt to set the standard norms for future reference. Other studies have also evaluated hair findings in different ethnic groups without, however, setting standard norms [5, 6].
Unfortunately, established norms for different ethnic and age groups from developing countries in general, and Egypt in particular, are lacking in the literature. The aim of this study was to establish the norms for measurable hair parameters of adult Egyptian females through trichoscopy.
Participants and Methods
The study included 90 volunteer Egyptian females with age ranging from 18 to 48 (mean ± standard deviation [SD] = 28 ± 8) years, during the period between February 2018 till May 2019. The study protocol was approved by Faculty of Medicine, Ain Shams University Research Ethics Committee (FWA 000017585). Participants gave a written consent to participate in the work after explanation of the technique and study performed.
The group under study was selected from patients visiting dermatology clinic at Ain Shams University hospital due to nonhair-related conditions, with no complaint of excessive hair shedding or family history of early hair loss. Females who had chemical hair treatment in the past 6 months, with severe systemic illness, with symptoms or signs of hair or scalp disease, as well as pregnant and lactating women within 6 months after delivery, or those with positive pull test were excluded from the study. Complete blood count, ferritin levels, and thyroid function tests were performed, and those with abnormal results were also excluded.
All volunteers were subjected to trichoscopy examination using FotoFinder Medicam 1000 videodermoscopy (FotoFinder F, Germany). The following set of standard images was registered for frontal, temporal, and occipital head regions: overview image; micro-image of ×20 magnification for qualitative inspection; 4 micro-images of ×50 magnification for statistical analysis.
All micro-images were registered using alcohol immersion liquid and nonpolarized light. The trichoscopy images were subjected to standard statistical processing using human-assisted algorithms of the TrichoLAB system.
The collected data were statistically analyzed using the statistical package for social studies (SPSS) version 16. Categorical variables were presented as number (N) and percentage (%). Continuous variables were presented as mean and SD. The norm's interval was set as the range of one SD from mean value, two-sided. Differences of continuous variables between frontal, temporal, and occipital areas were compared using repeated measures ANOVA. Statistical significance was determined as p < 0.05.
Results
Hair Density
The greatest hair density was observed in the frontal area, whereas the lowest was in the temporal area. There was a highly statistically significant difference between hair density in frontal and temporal areas (190 ± 29 vs. 154 ± 25/cm2; respectively, p < 0.01), and between density in occipital and temporal areas (180 ± 32 vs. 154 ± 25/cm2; respectively, p < 0.01). The difference between hair density in frontal and occipital area was statistically significant (p < 0.05) (Table 1).
Table 1.
Mean and range of evaluated trichoscopy parameter values (n = 90)
| Frontal area |
Temporal area |
Occipital area |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| mean ± SD | range1 | p value when compared to temporal | p value when compared to occipital | mean ± SD | range1 | p value when compared to occipital | mean ± SD | range1 | |
| Average hair density, N/cm2 | 189.5±28.8 | 160.6–218.3 | 0.000** | 0.022* | 154±24.9 | 129.7–179.5 | 0.000** | 180±32.2 | 148.6–212.9 |
| Average hair shaft thickness, µm | 62.7±8.4 | 54.3–71 | 0.000** | 0.008** | 59.8±8.7 | 51.2–68.5 | 0.114 | 60.9±7.8 | 53–68.7 |
| Thin (≤30 µm) hairs, % | 7.56±4.5 | 3.11–12.19 | 0.074 | 0.009** | 8.8±5.4 | 3.4–14.2 | 0.000** | 6.1±4.4 | 1.7–10.4 |
| Mid (30–50 µm) hairs, % | 21±8.9 | 12–29.9 | 0.009** | 0.000** | 23.8±10.1 | 13.7–33.9 | 0.287 | 24.8±11.5 | 13.3–36.3 |
| Thick (≥50 µm) hairs, % | 71.4±11.8 | 59.5–83.2 | 0.003** | 0.087 | 67.4±13.3 | 54.1–80.7 | 0.094 | 69.3±13.3 | 56–82.7 |
| Single follicular units, % | 21.75±5.6 | 16.1–27.4 | 0.372 | 0.000** | 22.6±6.9 | 15.6–29.6 | 0.000** | 15.9±4.8 | 11.2–20.7 |
| Double follicular units, % | 40.75±6.9 | 33.9–47.6 | 0.027* | 0.941 | 43.8±9.6 | 34.2–53.5 | 0.024* | 40.85±10.8 | 30–51.6 |
| Triple and bigger follicular units, % | 37.5±9.6 | 27.9–47.1 | 0.007** | 0.000** | 33.5±11.5 | 22–44.9 | 0.000** | 43.2±11.6 | 31.6–54.9 |
| Empty hair follicles/yellow dots, N/cm2 | 0.25±0.65 | 0–1 | 0.440 | 0.180 | 0.16±0.52 | 0–0.7 | 0.735 | 0.13±0.56 | 0–0.7 |
| Cumulative hair thickness, mm/cm2 | 11.8±2 | 9.8–13.74 | 0.000** | 0.002** | 9.17±1.6 | 7.6–10.7 | 0.000** | 10.9±2 | 8.8–13 |
| Number of follicular units, N/cm2 | 82.4±7.8 | 74.6–90.17 | 0.000** | 0.000** | 69.9±8.2 | 61.7–78.2 | 0.042* | 73.4±10.9 | 62.5–84.3 |
| Derived Sinclair scale | 2.14±0.27 | 1.9–2.4 | 0.000** | 0.002** | 2.6±0.29 | 2.28–2.86 | 0.000** | 2.27±0.31 | 2–2.6 |
The norms interval. Repeated measures ANOVA.
Statistically significant differences (p < 0.05).
Highly statistically significant differences (p < 0.01).
The norms for this parameter were 161–218/cm2 for frontal, 130–180/cm2 for temporal, and 149–213/cm2 for occipital area. Only the lower value is important from the clinical point of view; thus, norms for hair density were set as >161/cm2 in frontal, >149/cm2 in occipital, and >130/cm2 in temporal area (Table 2).
Table 2.
Summary of calculated norms in the study
| Frontal area | Temporal area | Occipital area | |
|---|---|---|---|
| Average hair density, N/cm2 | >161 | >130 | >149 |
| Average hair shaft thickness, µm | >54.3 | >51.2 | >53 |
| Thin (≤30 µm) hairs, % | <12.19 | <14.2 | <10.4 |
| Mid (30–50 µm) hairs, % | 12–29.9 | 13.7–33.9 | 13.3–36.3 |
| Thick (≥50 µm) hairs, % | >59.5 | >54.1 | >56 |
| Single follicular units, % | <27.4 | <29.6 | <20.7 |
| Double follicular units, % | 33.9–47.6 | 34.2–53.5 | 30–51.6 |
| Triple and bigger follicular units, % | >27.9 | >22 | >31.6 |
| Empty hair follicles/yellow dots, N/cm2 | 0–1 | 0–1 | 0–1 |
| Cumulative hair thickness, mm/cm2 | >9.8 | >7.6 | >8.8 |
| Number of follicular units, N/cm2 | >74.6 | >61.7 | >62.5 |
| Derived Sinclair scale | 1.9–2.4 | 2.28–2.86 | 2–2.6 |
Mean Hair Shaft Thickness
The greatest mean hair shaft thickness was observed in the frontal area. There was a highly statistically significant difference between hair shaft thickness in frontal and temporal areas (63 ± 8 vs. 60 ± 9 μm; respectively, p < 0.01), and between frontal and occipital areas (63 ± 8 vs. 61 ± 8 µm; respectively, p < 0.01) (Table 1).
The norms for mean hair shaft thickness were 54–71 μm for frontal, 51–69 μm for temporal, and 53–69 μm for occipital area. Only the lower value is important from the clinical point of view; thus, norms were set as >54 μm in frontal, >51 μm in temporal, and >53 μm in occipital area (Table 2).
Percentage of Thin, Mid, and Thick Hairs
The percentage of thin hairs (≤30 µm) observed in frontal, temporal, and occipital areas was 8% ± 5, 9% ± 5, and 6% ± 4, respectively. There was a highly statistically significant difference between percentage of thin hairs in frontal and temporal (p < 0.01), frontal and occipital (p < 0.01), temporal and occipital areas (p < 0.01) (Table 1). Norms were 3–12% for frontal, 3–14% for temporal, and 2–10% for occipital area. Only the higher value is important from the clinical point of view; thus, norms were set as <12% in frontal, <14% in temporal, and <10% in occipital area (Table 2).
The percentage of mid hairs (30–50 µm) observed in frontal, temporal, and occipital areas was 21% ± 9, 24% ± 10, and 25% ± 12, respectively. There was a highly statistically significant between percentage of mid hairs in frontal area and each of temporal and occipital areas (p < 0.01) (Table 1). Norms were set as 12–30% for frontal, 14–34% for temporal, and 13–36% for occipital area (Table 2).
The percentage of thick hairs (≥50 µm) observed in frontal, temporal, and occipital areas was 71% ± 12, 67% ± 13, and 69% ± 13, respectively. There was a highly significant difference between their percentage in frontal and temporal area (p < 0.01) (Table 1).
Evaluated norms for thick hair percentage were 60–83% for frontal, 54–81% for temporal, and 56–83% for occipital area. Only the lower value is important from the clinical point of view; thus, norms were >60% in frontal, >54% in temporal, and >56% in occipital area (Table 2).
Percentage of Single-, Double-, and Triple-Hair Units
The highest percentage of single-hair follicular units was observed in the temporal area (23% ± 7). There was highly significant difference between their percentage in temporal and occipital areas (23% ± 7 vs. 16% ± 5; respectively, p < 0.01) and between frontal and occipital areas (22% ± 3 vs. 16% ± 5; respectively, p < 0.01) (Table 1). Norms were set as <27% in frontal, <30% in temporal, and <21% in occipital area (Table 2).
The greatest percentage of double-hair follicular units was found in temporal area (44% ± 10). There was a statistically significant difference between their percentage in temporal and frontal area (44% ± 10 vs. 41% ± 7; respectively, p < 0.05), and between temporal and occipital area (44% ± 10 vs. 41% ± 11; respectively, p < 0.05) (Table 1). Norms were set as 34–48% for frontal, 34–54% for temporal, and 30–52% for occipital area (Table 2).
The occipital area had the greatest percentage of triple-hair follicular units (43% ± 12). There was highly significant difference between their percentage in occipital and frontal areas (43% ± 12 vs. 38% ± 10; respectively, p < 0.01), occipital and temporal areas (43% ± 12 vs. 34% ± 12; respectively, p < 0.01), and frontal and temporal areas (38% ± 10 vs. 34% ± 12; respectively, p < 0.01) (Table 1). Norms were set as >28% in frontal, >22% in temporal, and >32% in occipital area (Table 2).
Number of Empty Hair Follicles/Yellow Dots
Table 1 shows that the empty hair follicles/yellow dots were seen occasionally. The mean results were <1 in all areas with median 0. The norms for this parameter were only 1 for all areas (Table 2).
Mean Cumulative Hair Thickness
The mean cumulative hair thickness in frontal, temporal, and occipital areas was 12 ± 2 mm/cm2, 9 ± 2 mm/cm2, and 11 ± 2 mm/cm2, respectively (Table 1). Norms were set as >10 mm/cm2 in frontal, >6 mm/cm2 in temporal, and >9 mm/cm2 in occipital area (Table 2).
Mean Number of Follicular Units
The highest mean number of follicular units was observed in the frontal (82 ± 8/cm2), whereas the lowest was observed in the temporal area (70 ± 8/cm2) (Table 1). Norms were set as >75/cm2 in frontal, >62/cm2 in temporal, and >63/cm2 in occipital area (Table 2).
Derived Sinclair Scale
The highest score of derived Sinclair scale was in temporal area (2.6 ± 0.3), whereas it was 2.3 ± 0.3 in occipital and 2.1 ± 0.3 in frontal area. There was a highly significant difference between score in frontal and temporal area (p < 0.01), frontal and occipital area (p < 0.01), and occipital and temporal area (p < 0.01) (Table 1). The norms were set as 1.9–2.4 for frontal, 2.28–2.86 for temporal, and 2–2.6 for occipital area (Table 2). TrichoLAB trichoscopy image and report of a normal adult Egyptian female are represented in Figure 1.
Fig. 1.
TrichoLAB trichoscopy image and report of a 33-year-old Egyptian female with no symptoms or signs of hair or scalp disease.
Discussion
The documentation of the norms of measurable parameters allows accurate identification and treatment of what is abnormal. On establishing norms, age group, sex, as well as race should be considered. Most studies performing trichoscopy have focused on findings of various hair and scalp disorders [7, 8, 9, 10]. However, studies of established norms for different ethnic and age groups are limited in the literature.
In the present study, we established the norms for measurable parameters of hair in adult Egyptian females through examining 90 normal adult Egyptian females with age ranging from 18 to 48 years using videodermoscopy and TrichoLAB system processing. We observed the highest density of hairs in the frontal area and the lowest in the temporal area. Birnbaum et al. [5] evaluated hair densities in different ethnicities in a healthy American population using quantitative trichoscopic analysis and also found that Americans of African descent and Caucasians had highest hair density at the frontal scalp, whereas it was highest at vertex region in Hispanics. Hair density in frontal area in Egyptian females (190 ± 29/cm2) was greater than individuals of African (160 ± 27/cm2) and Hispanic (174 ± 32/cm2) descent, but less than in those of Caucasian descent (230 ± 33/cm2) [5]. In Americans of African and Hispanic descent, as well as Caucasians, the least density was found in the occipital region [5] which is in contrast to Egyptians in our study, where the least density was found in the temporal area.
On the other hand, the greatest hair density in adult Thai population was reported in the vertex area (163 ± 16/cm2) and the least in the frontal area (154 ± 13/cm2) [6]. Regarding average hair shaft thickness, we observed the greatest in the frontal area (63 ± 8 µm) which was similar to that reported by Rakowska [3], who observed the thickest hairs in the frontal area (61 ± 0.1 μm) in a population of 60 adult white females with mean age of 36.5 (19–64) years. However, she reported that the least thickness was found in the occipital area, whereas it was in the temporal area in our study. Similar to our findings, the frontal area had the thickest hairs (81 ± 5 μm) in adult Thais [6]. Thus, interestingly, adult Thais show greater hair thickness but lower hair density in all areas of scalp compared to Egyptians in our study.
Regarding racial differences, our findings support the diversity of hair density and diameter among different ethnic groups. It is believed that racial factors and genetic backgrounds are the main contributors to the follicular reservoir and hair counts, as well as the distribution of hairs [6].
In our study, percent of thin hairs (≤30 µm) was greatest in temporal (9% ± 5) and least in occipital (6% ± 4) areas. Rakowska [3] also reported the greatest percent of thin hairs (6.4% ± 5.7) in temporal area but the least in frontal area (5% ± 4.8). On the other hand, the percent of thick hairs (≥50 µm) was greatest in frontal (71% ± 12) and least in temporal areas (67% ± 13) in our study. Similarly, Rakowska [3] reported greatest percent of thick hairs (74% ± 13) in frontal region but least percent in occipital area (69% ± 17).
Rakowska et al. [11] reported that patients with female pattern hair loss had the least mean thickness of hair (47 ± 7 μm) and the greatest percentage of thin hairs (21% ± 12) in the frontal area. Therefore, a decrease in mean hair shaft thickness as well as increase in percentage of thin hairs in frontal region compared to occipital region may be considered an early diagnostic clue to female pattern hair loss. In healthy females in our study as well as in the study by Rakowska [3], the greatest average hair shaft thickness was observed in frontal area and the greatest percentage of thin hairs were noted in temporal area.
According to the number of hairs in pilosebaceous units, the highest proportion of single-hair units was observed in the temporal and the least in occipital area as has been reported by Rakowska [3]. The percentage of single-hair units is of special clinical importance as they are significantly increased in frontal area in patients with female pattern hair loss compared with the occiput (ratio above 2:1) [11]. Their percentage is also increased in telogen effluvium and various forms of anagen hair loss [12]. On the other hand, we demonstrated the greatest percentage of triple-hair follicles in the occipital area which is of special significance in hair transplant operations.
The Sinclair scale of hair midline density was introduced in 2005 and since then has become a popular tool to evaluate the severity of female pattern hair loss as it may be performed quickly and with no optical instrumentation. In 2019, Kasprzak et al. [13] proposed the term “Trichoscopy Derived Sinclair Scale” to describe the hair midline density as derived from trichoscopy and to differentiate this assessment of midline hair density from the traditional one based on visual inspection alone. “Trichoscopy Derived Sinclair Scale” is based on the very good correlation observed between Sinclair scale and the cumulative hair thickness density.
To sum up our findings, the frontal area demonstrated the highest number of hairs, the greatest average hair shaft thickness, the greatest percentage of thick hairs, greatest percentage of pilosebaceous units with double hairs, highest mean cumulative hair thickness, and the highest mean number of follicular units. Interestingly, the temporal area was found to have the highest number of vellus hairs and single-hair pilosebaceous units as has been reported by Rakowska [3]. In addition, we reported the least average hair shaft thickness, lowest number of hairs, as well as the least mean number of follicular units in temporal area. Collectively, these findings may contribute to physiological thinness of hair in temporal area. In comparison with results of Rakowska [3], Egyptian females had greater norms for mean hair thickness in all areas; greater percentage of thin hairs in all areas; similar norms for percentage of thick hairs in frontal area but higher norms for percentage of thick hairs in temporal and occipital areas; less norms for the percentage of follicular units with single hair in all areas; greater norms for the percentage of follicular units with triple hairs in all areas.
Conclusion
Norms of measurable parameters can be established using trichoscopy. Our results indicate that for healthy adult Egyptian females, not only are the average hair diameters and densities different in the different scalp regions but also the contribution of thin and thick hairs, as well as follicular units. Better understanding of the norms in clinical practice will help to detect what is abnormal in hair and scalp videodermoscopy.
Statement of Ethics
The study protocol was approved by Faculty of Medicine, Ain Shams University Research Ethics Committee, approval number (FWA 000017585). Participants gave a written consent to participate in the work after explanation of the technique and study performed.
Conflict of Interest Statement
The authors have no conflicts of interest to declare.
Funding Sources
This manuscript did not receive any funding.
Author Contributions
Hoda A. Moneib: idea and design of the work; critical revision of the article; final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Suzan A.K. Ahmed: data collection; drafting the article; final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Marwa S.E. Zaki: analysis and interpretation of data for the work; drafting the article; final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Data Availability Statement
All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.
Acknowledgments
The authors would like to thank Mr. Hubert Lacki, the TrichoLAB, and FotoFinder group for statistical processing of trichoscopy images free of charge.
Funding Statement
This manuscript did not receive any funding.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.