Journal of Dermatological Science (2005) 40, 187—193

Dermatoloqical

SCIENCE

www.intl.elsevierhealth.com/journals/jods

Skin ageing: A comparison between Chinese and European populations A pilot study

S. Nouveau-Richard^a, Z. Yang^b, S. Mac-Mary^c,L.Li^d, P. Bastien^a, I. Tardy^e, C. Bouillon^a, P. Humbert^c, O. de Lacharrière^a*

^a L'Oréal Recherche, Centre Charles Zviak, 90 rue du General Roguet, 92583 Clichy, France

^b Suzhou Medical University, Suzhou, China

^c CHU St Jacques, Besancon, France

^d West China Hospital, Sichuan University, Chengdu, China

^e Hôpital Franco-britannique, Levallois—Perret, France

Received 18 March 2005; received in revised form 28 May 2005; accepted 9 June 2005

KEYWORDS

Wrinkles;

Ageing;

Spots;

Chinese

Summary

Background: Although limited data are available, it is commonly considered that Europeans and Asians have different skin ageing features.

Objectives: The present studies have been carried out to evaluate the influence of age and sun-exposure on the main clinical signs of Asian skin ageing. Methods: One hundred and sixty Chinese and 160 French age-matched women (age range: 20—60 years old) were clinically examined and scored by the same dermatol­ogist. Facial wrinkles (crow's-feet, glabella and perioral wrinkles) and pigmented spots (on face and hands) were assessed in situ and standardized photographs of the face were taken. Lifelong sun-exposure was estimated from answers to a question­naire. Comparisons were made between 10-year age groups. Results: Results show that, for each facial skin area, wrinkle onset is delayed by about 10 years in Chinese women as compared to French women. Facial wrinkling rate over the years is linear in French women and not linear in Chinese women who appear to experience a fast ageing process between age 40 and 50. Pigmented spot intensity is a much more important ageing sign in Chinese women (severe for 30% of women over 40) than in French women (severe for less than 8% of women, irrespective of age). Conclusion: These first results underline that main skin ageing features (wrinkles, spots) progress differently in the Chinese and French women we have studied. They require to be confirmed on broad multicentre studies involving larger cohorts. © 2005 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.

* Corresponding author. Tel.: [phone]; fax: [phone]. E-mail address: [e-mail] (O. de Lacharriere).

0923-1811 /$30.00 © 2005 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.jdermsci.2005.06.006

1. Introduction

It is generally recognized that Asian and European skins age differently [1—3]. Identification of specific features of ageing process in each population is of prime interest to use most appropriate tools for evaluation and develop prevention measures and skin care products more adequately targeted to the spe­cific needs. Asian skin ageing has notably been inves­tigated by Korean [4] and Japanese studies [5,6].It was shown that the early onset of marked pigmented spots was more characteristic of skin ageing [7] than wrinkle development albeit the latter appeared to be a primary skin ageing sign [2]. However, there is no study providing a rigorous comparison of skin ageing in European and Asian populations. Reported com­parisons relied on the resultsof studies using different methodologies rather than on specifically designed trials to compare ageing signs in both skin types [8]. We therefore devised a specific study protocol to collect comparable skin ageing data in Chinese and French women in order to determine and quantify the skin ageing characteristics in each population. As it was important in our design to have one single inves­tigator in charge of all the clinical evaluations, we chose to begin with a pilot study involving a sample whose size was in accordance with such a design.

2. Subjects and methods

2.1. Study description

This two-fold study was conducted on two French and Chinese female populations in their respective country. In the initial part of the study, all women were examined in situ by the same dermatologist who also took photographs on each volunteer. Stan­dardized photographs were taken between Novem­ber and December 1999 in France and from late December 1999 to early January 2000 in China. In the second part of the study, the standardized photographs of all subjects involved in the study were clinically assessed by a second dermatologist.

2.2. Subjects

Three hundred and twentyhealthywomen including 160 in Besancon (France) and 160 in Suzhou (China) were involved in the trial after giving their informed consent and in full agreement with local ethics committees. They were distributed by age decade (age range: 20—30, 31—40, 41—50, 51—60, respec­tively) into four identical sub-groups of 40 volun­teers in each center.

2.3. Clinical investigation

It consisted of a clinical interview and a two-fold clinical assessment.

• The clinical interview was based on standardized questions on occupation, lifestyle and habits (smoking, sun-exposure). The skin phototype of French women was determined according to Fitz­patrick classification [9]. In Chinese women, only the facial skin complexion (fair, medium or dark) was assessed, due to the limits/deficiencies of Fitzpatrick classification when applied to non-Caucasian skin [10].

• In the first part of the clinical assessment, wrinkle intensity was determined in situ on three facial areas: the glabella, crow's-feet, and perioral areas. The clinical wrinkle severity score was determined using a 3-point grading scale: none, few and many wrinkles. Similarly, the intensity of benign facial pigmentation disorders was assessed using a 3-point scale: none, few and many pig-mented spots.

• In the second part, photographs of all subjects were assessed by a single dermatologist for wrin­kle intensity at crow's-feet and perioral areas. Standardized facial photographs of subjects were taken using a specific stereotactic photo device (Canfield Scientific, Inc., Fairfield, NJ). The posi­tion of face, lighting and distance from face to camera were invariable. A Nikon N6006 camera was used to take en face (1:6 magnification) and side views (1:4 magnification) focused on crow's-feet. Subjects were instructed to gently close their eyes and relax their face as much as possi­ble. The crow's-foot wrinkle severity score was designed using a 14-point photographic scale (0 for no wrinkle and 14 for maximal wrinkling inten­sity). The perioral wrinkle severity score was designed using a 9-point digital scale (0 corre­sponding to no wrinkle and 9 to maximum wrink­ling severity). The side of the face photographed was selected according to a pre-established ran­domization program. The same side of the face was used for the clinical assessment.

2.4. Statistical analysis

Wrinkle prevalence was compared by population (Chinese or French) and anatomical area using repeated measures analysis (areas) on binary data, with a GEE-type approach (generalized estimating equations), binomial distribution and a logit link function for the wrinkle answer (yes/no) variable. Wrinkle clinical score comparison was performed

using a Wilcoxon's distribution-free comparison test with the significance threshold set at 5%. Lastly, distribution of pigmented-spot classes according to age was performed using a Jonckheere—Terpstra distribution-free trend test with a 5% significativity.

3. Results

3.1. Population skin type

According to Fitzpatrick classification: 11% of the French women included in the study were of photo­type II, 74% of phototype III and 15% of phototype IV. Thirty-five percent of the Chinese women of the study had a fair skin complexion, 57.5% an intermedi­ate skin complexion and 7.5% a dark skin complexion.

3.2. Wrinkle onset and prevalence

Wrinkle onset and prevalence, determined in situ by age group and for each anatomical site, are shown on Fig. 1.

• The chronological onset of wrinkles by area was identical in both populations: crow's-foot wrinkles were the first to appear, followed by the glabella wrinkles and then by the perioral wrinkles. In the French women, wrinkle onset kinetics were signifi­cantly different according to area for the first two age groups. In the 20—30years age group, wrinkles prevalence was 50% for crow's foot, 32.5% for peri­oral area and 10% for the glabella (p = 0.0014). In the 31—40 years age group, the difference was still significant (p = 0.0002) but glabella wrinkles took prevalence over the perioral ones. Beyond 40 years of age, nearly all French women showed wrinkles in all three anatomical sites.

• In Chinese women, wrinkling starts at a later age. The site order in which wrinkles appeared was similar to that in French women but only became statistically significant according to anatomical site beyond 40 years of age. For the 41—50 years age group, wrinkles prevalence was 85.4% for crow's foot, 32% for perioral area and 54% for the glabella (p < 0.0001) and p = 0.011 in the 51 — 60 years age group.

• If wrinkle onset chronology was similar, the pre­valence according to the involved area was highly variable depending on the population group. Nearly 100% of French women in the 31—40 years age group presented wrinkles in the crow's-foot area versus less than 50% of Chinese women in the same age group (p < 0.0001). It is only in the 50-year-old age group that crow's-foot wrinkles were observed in 100% of Chinese women, prevalence differences further becoming not significant (p = 0.97). When age groups were matched, gla-bella and perioral wrinkle prevalence was always found lower in Chinese group than in French group. As regards the glabella, the differences were significant (p < 0.0001) except in both end groups, when all women showed no wrinkles or when all women had wrinkles. In the perioral area, the prevalence was always lower in Chinese women ( p < 0.005), irrespective of age group. • The increase rate of prevalence also was different in both populations. Between the 20—30 and 31— 40 years age group, the percent of French women showing crow's foot wrinkles doubles. In the gla-bella area, this percent increased from 10 to 70% during this age interval. Between 31—40 and 41— 50 years age groups, the prevalence of crow's foot wrinkles in Chinese women increased three-fold.

3.3. Wrinkle intensity

The age-related evolution of wrinkle intensity based on clinical scores assessed from the standardized

photographs, is instructive. Fig. 2a shows the mean perioral wrinkle intensity for each age group in both populations, Wrinkle intensity score was always higher in the French group than in the Chinese group. The difference becomes statistically signifi­cant as from age 30 (p < 0.001). Women in the 20— 30 years age group had too few perioral wrinkles for comparison to be relevant (p = 0.07). The mean score level of the 31—40 French women age group was only reached by the Chinese women of the 41 — 50 years age group. There is therefore a 10-year delay before Chinese women reach the same peri­oral wrinkle intensity score as French women.

A similar ageing difference was found between Chinese and French women in the 20—40 years age groups as regards crow's-foot wrinkles (p < 0.001) (Fig. 2b). Beyond 40 years of age, this difference seems to decrease rapidly (p = 0.019 for the 41—50 years age groups; and p = 0.5 for the 51—60 years age groups). If indeed the age-related increase in crow's-feet intensity score was linear in the French groups, it showed a sharp worsening between 41 and 50 years of age in Chinese women who ultimately caught up with mean score of French women. Beyond 50 years of age, both curves progressed in parallel with quite similar intensity.

3.4. Prevalence of pigmented spots

Pigmented-spot prevalence according to the level of importance and to age group is presented for French women (Fig. 3a) and for Chinese women (Fig. 3b). If overall spot-prevalence was relatively stable in all age groups in French women (p =0.097), it did pro­gress significantly with age in Chinese women (p = 0.001).

The number of women with no pigmented spots remained relatively stable in both groups until the age of 40. However, there were twice as many Chinese women without pigmented spots than French ones (40% versus 20%, respectively).

The most notable differences between both populations were found in women with few or many pigmented spots. Irrespective of age groups, most of French women (about 80%) had few spots, only 5% showed many. Conversely, a clearly greater number of Chinese women had many pigmented spots and the rate increased significantly with age. Thus, when Chinese women did have pigmented spots, they had much more than French women.

A sun-exposure impact was demonstrated in Chi­nese women. Those with many facial pigmented spots were clearly more often found among those having experienced frequent sun-exposure during childhood (62.2%) than those with a regular sun-exposure during childhood (37.8%). This distribution was not found again for current sun-exposure levels: 84% of women with many spots exposed themselves to sunlight regularly and 11% did so often.

Among the French women population of the study, there were too few women with many pig-mented spots (n = 6) to establish a link with sun-

exposure. Moreover, none of them had been fre­quently exposed to sunshine during childhood.

3.5. Impact of lifestyle on prevalence

3.5.1. Smoking

Hundred percent of the Chinese women of the study were non-smokers versus 70% of French women. Among the smokers, 75% smoked half a packet, 21% one packet and 4% two packets a day.

Wrinkle prevalence was always slightly higher in smokers but the difference never reached a signifi­cant level: 84% of non-smokers had wrinkles in the crow's-foot area versus 86% of smokers; 67% of non-smokers had wrinkles at glabella level versus 70% of smokers and 68% of non-smokers had perioral wrin­kles versus 72% of smokers.

3.5.2. Sun-exposure

Besancon and Suzhou have closely similar sunshine and rainfall levels (see Table 1). As a result, Chinese and French populations involved in the study were highly comparable as regards climatic conditions and environmental exposure. All the women included in the study worked indoors. Moreover, answers to the questionnaire established that over 80% of each population had a regular, but not intense, outdoor exposure. Extreme conditions (''never'' or ''very often'' outdoors) only regarded 3—5% of subjects.

4. Discussion

The original feature of this pilot study lies in its rigorous protocol. To our knowledge, it is the first time a skin ageing comparison has been carried out by the same clinician, on two different populations, in their respective country and within a relatively short time span. We were thus able to achieve quite comparable descriptions of both populations at a given time. Selecting two cities with similar climatic conditions allowed us to get rid of the effects of varying chronic UV exposures as far as possible.

Provided with identical standardized photography equipment, both centers were able to produce comparable photographic documents. A posteriori analysis of photographs allowed us to validate the evaluations made in situ.

A wrinkle onset chronology for various facial areas was thus demonstrated. In both populations, crow's-foot wrinkles appear first, followed by wrin­kles of the glabella and lastly in the perioral area. These results are in agreement with those we pre­viously obtained from a large multicentre study involving 2000 Chinese women [11]. They also agree with the results of a Korean study, which reported an anatomical site-related variation of the degree of wrinkle progression, with the same hierarchy (crow's-feet, then glabella) [12].

But this study also revealed new facts:

• It confirmed that Chinese women were affected by wrinkles later than French women, leading to large differences in terms of prevalence and severity. In the 31—40 years age group, the rate of French women with wrinkles in the crow's foot area was twice that of Chinese women. Up to 50 years of age, it was determined that the delay of onset at 10 years based on a same perioral wrinkle intensity score.

• We also demonstrated that there were popula­tion-related differences in the kinetics of increase in crow's-foot wrinkle severity. In French women, wrinkle severity followed a linear increase during ageing. In Chinese women, wrin­kle intensity appears to go through two stages with a low increase until the age of 50 followed by a fast increase period beyond. At the age of 60, both populations showed crow's-foot wrinkles of similar severity. These findings are in agreement reported by a Korean team [13].

• Skin hyperpigmentation data confirmed the importance of such disorders in Asian populations [2,7]. All benign pigmentation disorders were taken into account (freckles, senile lentigo, etc.) except blood-microcirculation related dis­orders, e.g. telangectasia, rosacea. Our study therefore provides an overall view of the phenom­enon. It allows us to go beyond plain presumption and to put figures on global differences between both populations. In addition to a clearly higher pigmented-spot prevalence in the Chinese group compared to the French group, analysis by age sub-groups revealed new data of interest.

• Unexpectedly, in the sub-groups before 40 years of age, there were more women with no facial pigmented spots in the Chinese sample popula­tion. However, in the same age groups, there were also more Chinese women having many pigmented spots. Between 20 and 40 years of age, Chinese women showed a more contrasted profile than French women who only had few pigmented spots for most of them. These observations agree with the results of several studies demonstrating that, in France, most women over 40 years of age have few pigmented spots whereas, in China, half of the women who have pigmented spots, have many. In Europe, it is only beyond 60 years of age that pigmented spots are numerous [14—16]. • Lastly, it appeared that the more frequent sun-exposure during childhood of women in the Chi­nese group was correlated to an increased number of pigmented spots at adult age. Unfortunately, this observation did not lead to draw a comparison between Chinese and French women, as none of the latter sample population had been frequently exposed to sunshine during childhood and too few French women (n = 6) showed many pigmented spots for a statistical link to be established.

The study was conducted so that all collected data were quite comparable. Besancon and Suzhou offer similar climatic conditions in terms of environmental conditions (sunshine and rainfall). Clinical examina­tions were performed by the same clinician. Skin ageing differences therefore cannot be attributed to an experimenter bias or to a meteorological factor or to major environmental exposure variations.

By considering that there is a relationship between Fitzpatrick skin type and complexion amongst white skin [9], it can be assumed that the distribution of the different skin complexions was not so different in the two populations. There was a higher rate of Chinese women with a fair skin complexion as was expected, and a higher rate of French women with a phototype IV (i.e., intermedi­ate skin complexion). Some studies have evaluated the phototype influence on wrinkling, and most of them showed that the difference existed between phototypes I—II skins and phototypes III—IV skins [15,17]: lower phototypes being more sensitive to skin aging. However, in another study, no relation was observed [4]. As distributions according to skin complexion in our study are comparable between the two compared populations, and even tend to include more fair skin in Chinese women, photo­type/skin complexion could not be considered as a significant factor involved in the differences we observed. As a result, skin type is not a major factor to account for the observed differences and intrinsic differences between European and Asian skins do seem to exist.

We currently lack elements to support clinical evidence as regards wrinkles development. In a Korean study, skin-ageing acceleration around the age of 50 was ascribed to the skin changes induced by menopausal oestrogen deprivation [13]. How­ever, such an increase in wrinkling at the time of menopause was not found in European populations [18] and could therefore represent an original fea­ture, specific to Asian skins.

Some published data provide support to explain the observed clinical differences regarding pigmen-ted spots. An ethnic group-related variation in melanosomes distribution was reported [19—23] showing a mix of individual (about 60%) and aggre­gated (about 40%) melanosomes in Asian skins, whereas aggregated melanosomes (85%) are prevail­ing in European skins [23,24]. The density and highly variable size of melanosomes in Asian skins could account for irregular, spotty pigmentation asso­ciated with photo-ageing.

5. Conclusion

The protocol designed for this study allowed us to compare skin-ageing process in European and Asian female populations exposed to similar environmental conditions. It notably allowed us to determine its clinical development with time; in both populations, wrinkles appear in the following order: crow's-foot area first, then glabella, then perioral area. However, the age of wrinkle onset was different. In Chinese women, it became apparent 10 years later in average and followed a non-linear progression. In French women, wrinkles appeared well before pigmented spots whereas the order was reversed in Chinese. Further, more Chinese women showed many facial pigmented spots at a very early age.

This pilot study thus provided consistent and relevant data to support previous hypotheses sug­gesting skin-ageing differences between European and Asian populations. It raises the need for and paramount interest of developing in-depth investi­gation of the chronology, prevalence and intensity of these clinical manifestations, which requires broad multicentre studies, integrating the ethnic and climatic diversity of continental China. We also need to identify the physiological features behind these differences so as to improve our approach of cosmetic repair and prevention from ageing altera­tions of Chinese women skin in order to most prop­erly meet actual, specific skin care needs.

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S. Nouveau-Richard et al.

Skin ageing in Chinese and European populations: a pilot study

Fig. 1 Wrinkle prevalence in the crow's foot (a), in the glabella (b) and in the perioral area (c) for the Chinese women (diamond) and the French one (square).

Fig. 2 Clinical intensity of perioral wrinkles (a) and crow's foot wrinkles (b) in French women (square) and Chinese women (diamond).

Fig. 3 Pigmented-spot prevalence in the French women's group (a) and the Chinese group (b) (light colour = no pigmented spot, mild colour = few pigmented spots, dark colour = many pigmented spots).

Data period: 1961—1990Besançon3SuzhoubMean annual sunshine1871.81976.4duration (h)Annual rainfall1108.51081amount (mm)

Table 1 Besançon and Suzhou climatic information

^a http://ufrmeca.univ-lyon1.fr/~gagnard/pageweb/ temp_norm /sommaire.htm.

^b http://www.hko.gov.hk/wxinfo/climat/world/eng/asia/ çhina/suzhou_e.htm.

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