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INTRODUCTION
Hair graying is a natural part of the aging processes1 and occurs in about 50% of the people after the age of 50 years2-4. However, premature hair graying is associated with pernicious anemia, osteopenia, thyroid disease, and several rare syndromes, such as progeria and Werner's syndrome5-9. However, most of people who develop gray hair are healthy and experience the usual life span of a given population.
Though gray hair itself is not a medical problem, it is a significant cosmetic concern. When adjusted for other variables, people with gray hair look older for their age10, and a portion of this population does dye the gray hair for aesthetic purposes. Therefore, behaviors surrounding hair dyeing reflect a desire for beauty and youth, and these behaviors are different across individuals according to their gender, age, race, the proportion of gray hair, etc. However, large epidemiologic study on hair dyeing has not been performed to-date.
In this study, we investigate the prevalence of hair dyeing in Korean subjects with gray hair.
MATERIALS AND METHODS
Study population
Upon study approval by the institutional review board (IRB No. H-0912-059-304), gray-haired subjects, without a pigment disorder or a hair disease other than patterned hair loss, were recruited at outpatient dermatology clinics at Seoul National University Hospital and at the Boramae Medical Center (Seoul, Korea). After informed consent, each subject was given a questionnaire and underwent physical exam.
Details of questionnaires and the physical examination
The extent of grayness was self-reported as follows: grade 1 (gray hair less than 20%), grade 2 (20% to 40%), grade 3 (40% to 60%), grade 4 (60% to 80%), and grade 5 (more than 80% gray hair). Data regarding demographic information (age and gender), hair dyeing and scalp skin diseases was also collected. The presence of scalp-related diseases were evaluated by physicians.
RESULTS
Demographic characteristics
Six hundred twenty subjects (330 men and 290 women) with gray hair were enrolled. All subjects were ethnic Koreans. The mean age was 50.8 years (±14.8), with a range from 15 to 91 years. The age distribution of gray hair between men and women were not significantly different (p>0.05). The mean of grayness grade from the survey was 2.1 (±1.3), and there were no significant differences between the grade reported by men and reported by women (p>0.05). Most subjects under 50 years of age had a grayness grade of 1 (Table 1).
Prevalence of hair dyeing in the subgroups
Of the 620 gray haired subjected total, 272 (43.9%) dyed their hair on regular basis. Dyeing behavior was significantly different across gender (p<0.001). In this study, lesser proportion of men (33.9%) dyed their hair than women, the latter among whom 55.2% of subjected dyed their hair regularly. Analysis by age revealed that only about 20% of subjects in their twenties or thirties dyed their hair to mask the gray hair, but this trend increased sharply to 60% among subjects of 50 to 69 years of age then decreased to <20% for those aged over 80 (Fig. 1).
Dyeing behavior seemed to be associated with individual subjective judgments of the extent of graying (Fig. 2). The prevalence of hair dyeing was only 22.4% among subjects who considered the gray hair to be less than 20% of the total amount (grade 1), but the prevalence exceeded 60% among subjects who thought more than 20% of their hair was turning gray (over grade 2). This difference was significant (p<0.001).
The prevalence of hair dyeing was not significantly different between the non-hair loss group and the patterned hair loss group, that is, 43.8% dyed hair in the non-hair loss group and 44.1% in the hair loss group (p>0.05; Table 2).
Relation between hair dyeing and scalp diseases
At the time of survey, each study subject was evaluated for the presence of scalp discomforts, such as an itching sensation, pain, or increased scale, and was interviewed regarding any previously diagnosed skin disease of the scalp. Based on the presence of scalp disease, subjects were then classified into two, non-scalp disease and scalp disease, groups. The prevalence of hair dyeing was not significantly different in these two groups (p>0.05), that is, 45.6% of those in the non-scalp disease group and 37.7% in the scalp disease group dyed their hair (Table 3).
DISCUSSION
The incidence of graying is known to be similar for men and women2, and our survey confirms that this to be true among the Korean population. However, hair dyeing prevalence was found to be highly dependent on gender, suggesting that women are more concerned about graying than men in Korea. This interpretation can be used to explain differences in hair dyeing behaviors among subjects with different grades of graying. Individuals who feel graying has advanced to more than 20% of the total hair were more likely to be concerned about graying, and thus, were more likely to dye their hair.
Our survey revealed that hair dyeing is more common for people over the age of 40 years than among people in twenties or thirties. We believe this is also reflects different levels of concern regarding hair graying among different age groups. In Korea, the onset of graying normally occurs in the third or fourth decade of life11. A previous report published in Korea did reveal that 62.7% of 1,499 university freshmen had their hair dyed at least once in their life12, but this prevalence figure was determined without the purpose of hair dyeing in study design, whereas the current study was limited to hair dyeing specifically for masking of gray hair, which would explain why our results indicate a much lower hair-dyeing prevalence among the younger population.
Furthermore, we have found that the proportion of people who dye their hair decreased to less than 20% after the seventh decades of life, which indicates that subjects over 80 usually do not mind the gray hair as gray hair is considered socially acceptable for this age group in Korea. In addition, we have found that the prevalence of hair dyeing is not dependent on hair loss, which indicates that hair dyeing behavior is not affected by existing hair loss. In fact, hair loss was reported not to be significantly correlated with graying11.
Few studies have suggested that the components of hair dye can cause allergic contact dermatitis of the scalp13,14. However, we did not observe any increase in the prevalence of scalp disease, including contact dermatitis, amongst those subjects who dyed their hair (Table 3). Thus, hair dyeing did not significantly correlate with the presence of a scalp disease (odds ratio=0.72). p-Phenylenediamine is a component of hair dye and a well known allergic contact sensitizer15, but recent hair dyes have been developed without sensitizing agents like p-phenylenediamine, ammonia, paraben, mineral oil, or benzophenone. Many patients who are sensitized to p-phenylenediamine have undoubtedly benefitted from these alternative hair dyes16, and this may explain why hair dyeing was not found to be associated with an increase in the prevalence of scalp disease or contact dermatitis among the subjects enrolled in this study.
Hair dyeing is performed as a routine part of everyday life for a large proportion of the aging population, but few studies have been conducted on its prevalence. In the current study, we found that Korean women, people in their fifties and sixties, and people with more than 20% extent of grayness were more likely to dye their hair than otherwise. We believe that these findings would be helpful to clinicians, researchers in pharmaceutical field, and the general public.
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