Chapter 14 461 Table 4. Hair Fiber Diameters versus Age for Japanese men and women15* Predicted Diameter(µm) Calculated Area of Cross-section (µm2) Age Men Women Men Women 15 84 79 5542 4902 20 84 80 5542 5027 25 83 82 5411 5281 30 81 82 5153 5281 35 79 82 4902 5281 40 76 82 4536 5281 45 72 81 4072 5153 50 68 78 3632 4778 55 63 75 3117 4418 *Data points were read from a graph in this paper by Otsuka and Nemoto and predic- tion equations calculated. The data points for diameters of this table are from the pre- diction equations which were all within ± 1% of the graph data points, which were then rounded off to the nearest micrometer. Cross-sectional areas were calculated from the predicted diameters assuming circularity and average diameters. The second largest study on age versus diameter was by Robbins and Dawson et al.16 who measured average optical fiber diameter on 250–400 hairs in each of two sites in the parietal region of 1,099 Caucasian females ages 18–66 with self-perceived hair loss. The age for maximum diameter for these Caucasian females was calculated from both quadratic and cubic models to be 43–46 years of age, as seen in Figure 1. This peak in fiber diameter with age is in reasonable agreement with the study by Otsuka and Nemoto. Several smaller studies on age versus fiber diameter were conducted by Tajima et al.17, Nagase et al.18, Trotter and Dawson19,20, Ebling21, Jackson et al.22, and Birch et al.23 The data by Tajima et al. examined hair 40 mm from the coronal midline on the scalp to the ear. When modeled by a cubic equation, this study shows the maximum diameter for 113 Japanese females, ages 14–68, with little to no hair loss, to be in the low-forties (age 43). A graph in the Tajima paper shows the maximum diameter for these 113 women