Evaluation of the Scalp Hair Mass of Koreans

Park, Jin; Ihm, Chull Wan

Abstract

BACKGROUND
Hair researchers in medical science have focused on the biology of a hair, but the general population and the patients with alopecia are concerned about their total external hair mass or the hair volume of the head. There have been many reported papers on hair, yet it is difficult to find papers that have evaluated the total hair mass of the head of normal persons.
Objective
We wanted to assess the total scalp hair mass and its parameters by which the hair mass is made.
METHODS
For 42 volunteers (22 males and 20 females, age range: 23 to 31 years old), the volume of total scalp hair mass was assessed by its total number of hairs, its density and the diameter of the hair via a unit area trichogram with performing dermoscopy and light microscopy. The proportions of terminal/intermediate/vellus hair, the anagen/non-anagen ratio and the growth rate of the scalp hairs were also assessed. The correlations of the hair length and the diameter were measured for 603 hairs taken from 14 alopecia areata patients only when they showed regrowth of normal hair.
RESULTS
The results are summarized as follows. The total number of scalp hairs was 112,000 (males: 116,000, females: 106,000) with no statistical difference between genders. The average size of the scalp was 694.4 cm2 (727.4 cm2 in males and 658.0 cm2 in females) with a statistically larger size for the males. The average scalp hair density of the males and females was 159.7/cm2 (153.0/cm2 at the temporal area (T) and 166.5/cm2 at the parieto-occipital area (PO)) with no statistical difference according to gender. The average diameter of the scalp hair was 87.0micrometer: 84.9micrometer (86.0micrometer in males and 83.6micrometer in females) in the T and 89.0micrometer (89.4micrometer in males and 88.5micrometer in females) in the PO with no statistical difference according to the area of the scalp area or gender. The proportions of terminal/intermediate/vellus hair (%) were 86.5/8.8/4.7 and the proportions of anagen/non-anagen (%) hairs were 89.6%/10.4% with no statistical difference according to the area of the scalp area or gender. The time for new hair to emerge on the surface of the scalp after epilation was about 68.5 days with no statistical difference according to the area of the scalp or gender. After the hair emerged on the skin surface, the average growth rate for the first 1 month was 0.172 mm/day and 0.248 mm/day during the following month, and 0.35 mm/day thereafter. It took about 4 months for the newly emerging hair to reach 1 cm from the scalp surface. The correlation between the length and diameter of hair with assessing 603 hairs of the 14 alopecia areata patients in their recovery phase was as follows: the hair less than 10 mm in length showed a diameter of 20~40micrometer. It reached 60micrometer when the hair grew up to 18 mm in length. The diameter reached around 87micrometer when the length of the hair exceeded 35 mm and then the diameter kept its value.
CONCLUSION
We numerically measured the various parameters of the hair mass of the head of normal Koreans in their twenties.