ObjectiveTo reveal the characteristics of hair involvement under different subtypes of androgenetic alopecia (AGA) patients in China, so as to provide a scientific basis for clinical diagnosis and treatment as well as related research.

MethodsThe subjects of this study were AGA patients and healthy individuals recruited by the Department of Dermatology of Peking University People′s Hospital from November 2019 to January 2020. Multi-area trichoscopy images were analyzed using specialized software to quantitatively assess hair count, hair diameter and diameter distribution, and the number and distribution of hair follicle units. The data of hair density, hair diameter, hair follicle unit density, and single hair follicle unit ratio etc. in frontal angle, vertical, temporal and occipital area were obtained, and statistical analysis was conducted.

ResultsA total of 64 patients with AGA and 29 normal subjects were included in this study, including 37 male pattern hair loss (MPHL) patients and 27 female pattern hair loss (FPHL) patients. The hair density in frontal angle, vertex, temporal and occipital of MPHL patients were (127.61±19.03),(134.43±25.88), (92.01±15.70), (122.82±16.56)/cm ², respectively. The hair diameter were (53.56±8.45), (53.10±11.37), (64.34±6.39), (64.83±7.21)μm, respectively. The density of single hair follicle unit were 32.57%±11.30%, 29.78%±14.56%, 21.25%±13.10%, 15.69%±9.30%, respectively. The hair density of the corresponding parts of FPHL type patients were(112.47±14.37), (123.25±19.50), (94.19±26.19), (114.73±20.98)/cm ²; respectively. The hair diameter were (54.87±7.00), (54.74±8.91), (58.69±10.25), (62.40±11.34)μm, respectively. The ratio of single hair follicle unit 42.11%±13.84%, 32.52%±15.17%, 27.35%±14.42%, 20.18%±11.03% respectively. There was no significant difference in hair density between the MPHL group and normal control. The diameter of hair in the frontal angle and the vertex area of MPHL group was significantly lower ( P<0.05), and the ratio of single hair follicle unit in the vertex area was significantly lower ( P<0.05). The hair density in the vertex and occipital area of FPHL patients was significantly lower than normal control ( P<0.05) and the hair diameter in the frontal angle, vertex and temporal regions was significantly lower ( P<0.05). The ratio of terminal hair and vellus hair was also significantly different as well, and the ratio of single hair follicle unit in the four areas were significantly higher than normal control ( P<0.05). The hair involvement of MPHL patients was mainly in the frontal angle and vertex area, while FPHL patients were mainly in the vertex area with varying degrees of involvement in all parts. The hair diameter of the main affected parts of MPHL and FPHL were closely related to the severity of the disease, with a significant increase in the single hair follicle unit ratio ( P<0.05).

ConclusionsThe basic features of hair involvement in Chinese AGA patients were revealed by digitized trichoscopy analysis, which mainly showed a decrease in the diameter of hairs (diameter heterogeneity) and an increase in single hair follicle unit ratio.There were significant differences in the sites of hair involvement between patients with MPHL and FPHL, with FPHL displaying a more prominent diffuse involvement feature.