P5.55 CHARACTERIZATION OF JAPANESE SENILE GRAY HAIRS.

Ritsuro Ideta¹,Haruhi Iwaki¹,Yousuke Nakazawa¹, Rumiko Toyama¹, Tsutomu Soma¹, Akihiro Ishino¹, Masahiro Tajima¹, Kensei Katsuoka²

¹Shiseido Research Center, Yokohama , Japan, ²School of Medicine, Kitasato University, Sagamihara , Japan

Hair graying may be caused by aging, undergoing stress and hereditary predispositions, it is one of the typical senile changes. It is also considered a cosmetic problem, especially for women and younger people. However, few reports regarding the characterization of gray hair have been published. Therefore, we investigated the characteristics of gray hair in Japanese subjects. The subjects consisted of 21 male and 16 female Japanese volunteers with gray hair, aged between 33 to 69 years old. Gray hair ratios and hair diameters were measured in video microscope images on four areas on the scalp (vertex, left and right temporal and occipital regions). Gray hairs were classified by fixed gray scale on the images. The hair samples were isolated from the same areas and the diameters of the hairs were measured in micrometers by measuring the cross-sectional photo-images of the samples. The gray hair ratio was lower on the occipital area than those on the other three areas. Hairs with under 60 micrometers of diameter tended to have lower graying ratios than hairs with diameters over 60 micrometers. No statistical difference was observed for the growth ratio and number of anagen hairs between gray hairs and pigmented hairs with over 60 micrometers of diameter. The shapes of the cross sections of most hairs (about 80%) were round or oval but some hairs had polygonal shapes. The ellipticies (ratio of minor axis to major axis) were about 0.8 and it was higher than that of Caucasian hairs reported previously. Taken together, in Japanese subjects, the gray hair ratio was lower on the occipital regions on the scalp and the numbers of thinner hairs were lower compared to the pigmented hairs. From these results, the color of the hair might correlate with its physical properties. Further study is needed to elucidate whether melanization activity in the hair follicles affect the shapes of hairs physiologically.