Characteristics of skin aging in Korean men and women
Authors: Chung J. H. 
Published: September 2010

Introduction

Korea is located between Japan and Mainland China. The people of these three countries have similar appearances and it is difficult to differentiate between them. Although the population of Asia is more than half of the total population of the Earth, the inherent characteristics of Asian skin have not been well investigated. Commercial markets for cosmetics and drugs for photoaged skin are rapidly expanding in many Asian countries. Therefore, many investigators in the field of dermatology and cosmetology have become interested in brown Asian skin.

Clinical characteristics of skin aging and photoaging in Asians

Skin aging can be divided into two basic processes: intrinsic aging and photoaging [1]. Intrinsic aging is characterized by smooth, dry, pale, and finely wrinkled skin, whereas photoaging, which indicates premature skin aging in chronically photodamaged skin, is characterized by severe wrinkling and irregular pigmentation. The pattern of wrinkling in Asians seems to differ from that in Caucasians. Asians have coarser, thicker and deep wrinkles, particularly in the forehead, perioral and Crow's foot areas. In contrast, Caucasians usually have relatively fine cheek and Crow's foot wrinkles. The reasons for these differences are not known and need further investigation.

There are racial, ethnic and genetic differences, and differences of skin structure and function, between the brown skin of Asians and the white skin of Caucasians. As Asian skin is more pigmented, acute and chronic cutaneous responses to UV irradiation differ from those in white skin. Many people believe, based on clinical impressions, that the main process of photoaging in Asians involves pigmentary changes, rather than wrinkling. However, no study has been performed to confirm this belief.

Risk factors for skin wrinkles and their relative risks in Korean skin [2]

Various factors such as age, sun‐exposure, and smoking are known to be important risk factors for wrinkles. However, the relative risks of each factor on wrinkles in the brown skin of Asians have not been investigated, and they could differ from those in Caucasians.

An evaluation system for skin wrinkling is necessary for Asian skin [3]. Thus, we developed an eight‐point photographic scale for assessing wrinkles in both Korean genders [2]. This scale can probably be applied to the populations of other Asian countries, at least to the Japanese and Chinese. The pattern of wrinkles in both genders appears to be similar.

Age

Age is an important risk factor for wrinkling in Asians, as in Caucasians. Korean subjects in their 60s showed a 12‐fold increased risk of wrinkling, while subjects in their 70s have a 56‐fold increased risk compared with young age group.

UV light

It is well known that the UV component in sunlight can cause and accelerate photoaging. The pigmented skin of Asian may better protect skin from acute and chronic UV damage. However, we found a strong association between sun‐exposure and the development of wrinkling in Koreans. It was found that sun exposure of more than 5 h per day was associated with a 4.8‐fold increased risk in wrinkling versus less than 2 h of sun‐exposure in Koreans.

Estrogen deficiency

Korean females have more wrinkles than men, after controlling for age, sun exposure, and smoking, it was found that they have a 3.6‐fold increased risk of developing wrinkles than their male counterparts [2]. It has also been reported, that the relative risk for wrinkling in women is higher than in men as for in white Caucasians [4]. The reason why women show more wrinkles remains to be determined. It is possible that a reduction in skin collagen because of estrogen deficiency in postmenopausal woman may aggravate wrinkling severity. Korean women with more than 10 years since menopause showed a 3.9‐fold higher risk of wrinkling than the women 5 years of beyond menopause [5]. We demonstrated that women with a history of HRT have a significantly lower risk, more specifically, one fifth of the risk of facial wrinkling relative to those who had no history of HRT. Interestingly, we found that wrinkle severity significantly increased with an increasing number of full term pregnancies. The relative risk for severe wrinkling is increased by approximately 1.8‐fold per full term pregnancy.

Smoking

It is known that smoking causes skin wrinkling in Caucasians, and that it plays no role in Blacks [6, 7]. Koreans with have a smoking history of more than 30 pack years showed a more than 2.8‐fold increased risk of wrinkles [2]. The relative risks of wrinkles associated with a 30–50 pack‐years history of smoking were 2.8‐ and 5.5‐fold, respectively.

Dyspigmentation in Asian skin

To follow pigmentary changes, six photographic standards for both genders were developed for Korean skin, to produce a 6‐point scale [2, 8]. Hyperpigmented spots, mostly lentigines, were prominent among women, while seborrheic keratosis tended to be more prominent in men.

Seborrheic keratosis in Korean men

Seborrheic keratoses (SKs) are benign cutaneous tumors. They have diverse clinical and histopathological appearances and are very common in the elderly (over 50 years old). The etiology of SKs is not well understood, although patients with a great number of lesionsshow a familial trait with an autosomal dominant pattern, and human papilloma virus has been suggested as possible cause because of verrucous appearance of the lesions. Exposure to sunlight has been suggested to be a risk factor for SKs. However, there is still some debate in terms of the role of sunlight. Recently, we have investigated the clinical characteristics of SKs and relationship between SKs and sunlight exposure in Korean males [9].

The prevalence of SKs in Koreans increases with age; it rose from 78.9% at 40 years, to 93.9% at 50 years and 98.7% in those over 60 years. Exposed areas, i.e. the face, neck and dorsum of the hands, demonstrate a significant increase in the prevalence of SKs by decade, whereas partly exposed areas, although SKs tended to increase in prevalence with age, this trend was not significant. When the estimated body surface area (BSA) is taken into account, the number of SKs on both the face and dorsum of the hands (0.51 ± 0.08 per 1% BSA) was over‐represented compared with the trunk. SKs were also concentrated on the neck (0.38 ± 0.07 per 1% BSA) and in the V‐area (0.47 ± 0.09 per 1% BSA). Outer forearms also showed 3‐fold more SKs per unit area than neighboring arms and inner forearms, which are classified as partly exposed area (0.09 ± 0.02, 0.03 ± 0.01, respectively). The total area covered by SKs on exposed area also became significantly larger with aging than on intermittently exposed areas. These results indicate that exposure to sunlight might be related to SK growth.

Our results indicated that excessive sun exposure is an independent risk factor of SKs. After controlling for age, smoking, and skin type, subjects with a sun exposure history of more than 6 hours per day showed a 2.28‐fold increased risk of having severe SKs (n ≥ 6) compared with those exposed for less that 3 h per day. These findings indicated that sun‐exposure may play an important role in SK development.

In summary, SKs are very common in Korean males and represent one of the major pigmentary problems. SKs concentrate on exposed skin, especially on the face and dorsum of the hands. Both age and lifetime cumulative sunlight exposure are important contributing factors and may work in a synergistic manner.

Conclusion

Many people tend to believe that wrinkles are not a prominent feature of Asian photoaged skin, and that dyspigmentation is a major manifestation in Asian skin. Contrary to this impression, wrinkling is also a major problem in the photoaged skin of Asians, and Korean people showing severe pigmentary changes usually tend to have severe wrinkles. In conclusion, the wrinkling patterns and pigmentary changes of photoaged skin in East Asians differ from those of Caucasians, and the relative risks of aggravating factors may be different from those of Caucasian skin.

References

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