The comparison of the melanin content and UV exposure affecting aging process: seven countries in Asia.

Background: The skin brightness is determined according to the amount and type of melanin. People with darker skin have a greater amount of melanin that makes their skin less susceptible to UV damages. They live in lower latitude and receive a greater amount of the intensity of the UV radiation.

Aim: We wanted to know how the latitude and skin brightness affect skin aging.

Methods: Three thousand volunteers from seven countries (Korea, China, India, Thailand, Vietnam, Indonesia, and Malaysia), aged 20-59 years, participated in this study. We measured skin brightness, Ra (wrinkles parameter), and R2 (elasticity parameter) under controlled environmental conditions. The skin brightness of the face was measured using the Janus which is a facial analysis system. Cutometer the elasticity was measured by on the cheeks, and PRIMOS lite was used to evaluate wrinkles on crow's feet.

Results: Latitude and skin brightness showed a positive correlation (0.346). Also, the correlations of Ra and R2 with skin brightness were significantly negative (-0.181) and positive (0.105), respectively. Results of comparison of Ra and R2 with age among the countries showed no significant difference among the 20s, but there was a significant difference among the 50s between countries with high latitude and low latitude.

Conclusion: The long-term exposure of UV radiation, the natural environmental factor, seems to have more decisive effect on the skin aging process than the photoprotective effect of melanin of epidermal skin. This study helps to understand differences of the skin properties among countries in Asia.