Chapter 14 459 the center minimum diameter of the dark fibers were slightly larger than those of gray hairs. So whether gray hairs are coarser than highly pigmented hairs remains in question and needs further investigation. Knowledge gaps for hair graying and age: To date, we have not been able to find any literature on graying and scalp hair density versus age, therefore further investigation will be required to determine whether these factors are related. As stated above, there is conflicting evidence in the literature as to whether gray hairs are coarser or finer than highly pigmented hairs, and additional large studies are required to resolve this debate. Another important knowledge gap for hair graying and age is the paucity of data for Asian and African populations, which precludes a direct comparison of the rate of graying versus age in these geo-ethnic groups with that of Caucasians. Fiber Properties—Part II: Non-color Scalp hair diameter versus age: Women, men and ethnicity: Infancy through childhood for males and females: Trotter and Duggins,13 in their study of scalp hair from infancy through childhood, reported cross-sectional areas on the same 14 Caucasian subjects from 1 month through 10 years of age. We calculated mean fiber diameters from this study and arrived at data summarized in Table 3. We also analyzed this same study’s data by the matched pairs test showing highly significant differences at 1 month, 7 months, 2 years, and 3 years from all other ages. Several of the other pairs were not significantly different as indicated by the connecting lines in this table. Clearly, the diameters are smallest at 1 month. They are also smaller at 7 months, 2 years, and 3 years compared with all other ages. Larger changes in diameter occur between 1–7 months and 7 months and 2 years compared to the total change that occurs between 4–7 years of age. These dimensional changes in the hair fiber correspond to the generalized description by Furdon and Clark14 that the fine hair of infants tends to be lost by about the
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