Akihiro Ishino

Progressive decrease in hair diameter in Japanese with male pattern baldness.

Fifty‐six Japanese with male pattern baldness were evaluated for changes in their hair diameters over three years. The mean hair diameter significantly decreased each year. The average decrease was 1.1 μm per year. Although the percentage of vellus hair increased by 3.6% over three years, this increase rate was lower than that found in Caucasians. To precisely examine the change in hair diameter, the mean distribution of this diameter was investigated. At the beginning of the study, clear peaks were observed at 95 μm in the twenties and 45 μm in the fifties. The number of thicker hairs decreased and the high frequency peak shifted to a thinner hair diameter over 3 years.

Quantitative evaluations of male pattern baldness

Several methods for the evaluation of hair growth have been reported; however, none of the hitherto reported methods are satisfactory as unbiased double blind studies to evaluate the efficacy of hair growth agents. In the present paper, we describe quantitative evaluation methods for hair growth by measuring the anagen ratio and hair diameters in 56 Japanese subjects aged 23-56 for 3 years. The average anagen ratio decreased by 3.8% in 3 years. The average hair diameters showed a statistically significant decrease each year totalling 3.4 microns. Subjects were sorted according to their anagen ratio into 4 groups. Each group showed different distribution patterns of hair diameters. The higher anagen ratio group has a high frequency peak at thicker hair diameters and the lower anagen ratio group has a high frequency peak at thinner hair diameters. The number of thicker hairs decreased and the high frequency peak shifted to thinner hair diameters in 3 years. These methods are useful to evaluate both the progression of male pattern baldness and the effects of hair growth agents with double blind studies in an unbiased quantitative fashion.