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Quantification of Age-Related Facial Wrinkles in Men and Women Using a Three-Dimensional Fringe Projection Method and Validated Assessment Scales
Article first published online: 25 NOV 2013
© 2013 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.
Volume 40, Issue 1, pages 22–32, January 2014
How to Cite
Luebberding, S., Krueger, N. and Kerscher, M. (2014), Quantification of Age-Related Facial Wrinkles in Men and Women Using a Three-Dimensional Fringe Projection Method and Validated Assessment Scales. Dermatologic Surgery, 40: 22–32. doi: 10.1111/dsu.12377
- Issue published online: 6 JAN 2014
- Article first published online: 25 NOV 2013
Whereas the molecular mechanisms of skin aging are well understood, little information is available concerning the clinical onset and lifetime development of facial wrinkles.
To perform the first systematic evaluation of the lifetime development of facial wrinkles and sex-specific differences using three-dimensional (3D) imaging and clinical rating.
200 men and women aged 20 to 70 were selected. Wrinkle severity of periorbital, glabellar, and forehead lines was evaluated using 3D imaging and validated assessment scales.
Wrinkle severity was greater at all assessed locations with older age. In men, wrinkles manifested earlier and were more severe than in women. In women, periorbital lines were the first visible wrinkles, in contrast to the forehead lines in men. In both sexes, glabellar lines did not clinically manifest before the age of 40.
The results of the present study confirm a progressive increase of crow's feet and forehead and glabellar lines in men and women. Although the development of facial wrinkles happens earlier and is more severe in men, perimenopause seems to particularly affect development in women. Clinical ratings and 3D measurements are suitable methods to assess facial wrinkle severity in men and women.
Attractiveness and beauty play an important role in modern human society. Facial attractiveness is mainly characterized by youth and symmetry, as well as even skin texture and pigmentation.[1, 2] Aging strongly affects these parameters. One of the most visible and obvious morphologic changes of aging is the development of facial wrinkles. A large number of dermatologic procedures have been developed to maintain the youthful appearance of skin, which has become an important aspect of dermatologic research and cosmetic science.[4, 5]
Over the last few decades, a number of theories regarding skin aging have been published, mainly addressing the histologic and molecular perspectives of skin aging. It is commonly accepted that the combination of several mechanisms contributes to skin aging, including oxidative stress, mitochondrial dysfunction, telomere shortening, and various genetic mechanisms.[3, 6] Along with these intrinsic molecular mechanisms, environmental influences, in particular solar ultraviolet (UV) radiation, triggers skin aging. Increased production of reactive oxygen species due to UV radiation alters gene and protein structure and function. Intracellular and extracellular homeostasis modifying cellular behavior and cell–matrix interactions lead progressively to a loss of structural integrity and physiologic function.[6, 7] This knowledge led to the classification of two distinct entities of skin aging: photo-aging and chronological skin aging.[8, 9]
Whereas the level of knowledge regarding molecular and histologic mechanisms of skin aging is high, there is still a lack of information regarding the clinical genesis of wrinkles. It is widely accepted that wrinkles and furrows become prominent in the fourth to fifth decade of life, with a continuous increase in wrinkle severity with aging.[3, 7] Although a few studies of the clinical manifestation of facial wrinkles have been published,[7, 10] knowledge about life-time development of wrinkles and their dependence on age, location, and sex is vague and nonspecific.
The aim of the present clinical study was to conduct the first systematic assessment of the lifetime development of facial wrinkles. Two hundred women and men were enrolled following strict criteria including age, sun behavior, and smoking habits. Wrinkle severity of crow's feet and glabellar and forehead lines was evaluated using the three-dimensional (3D) fringe projection method (PRIMOS) and 5-point photonumeric validated assessment scales (VAS). A further aim of the study was to assess sex-specific differences in the life-time development and severity of facial wrinkles.
Material and Methods
Two hundred healthy women and men with Fitzpatrick skin types I to IV aged 20 to 70 participated in this clinical study after providing written informed consent. The 150 men and 50 women were distributed evenly into five age groups (Table 1).
All volunteers were required to be free of skin disease or any other physical disorder with cutaneous manifestation. Subjects were of skin type I through IV and without a history of frequent sunburns (≥10 throughout life). Exclusion criteria were distinct signs of extrinsic skin aging (e.g., deep furrows, altered pigmentation) due to UV radiation (sun or tanning beds) and strong smoking habits (≥20 cigarettes/week over >2 years). Subjects who had had any minimally invasive (e.g., botulinum toxin, chemical peels, fillers) or invasive (e.g., face lift) treatment in the measurement area were not included in the clinical trial. Women in groups I through III were in the follicular phase (days 1–14) of their menstrual cycle, whereas subjects in groups IV and V confirmed in a personal interview that they were postmenopausal (≥12 months without menstrual flow) and without hormonal replacement therapy.
Washing skin, applying cosmetics, sport activities, and sauna use were not allowed for at least 12 hours before measurements.
A 5-point photonumeric VAS and the 3D digital fringe projection method (PRIMOSpremium, GFMesstechnik GmbH, Berlin, Germany) were used to assess skin topography. Standardized photography was performed (mediscope, FotoFinder Systems GmbH, Bad Birnbach, Germany). Images were taken after subjects acclimatized for 30 minutes at 20°C and 50% relative humidity.
Fringe Projection Method
One of the most up-to-date methods for the 3D evaluation of skin topography in real time is the digital fringe projection method, which is based on the digital projection of a striped pattern in a defined angle onto the skin in vivo. By analysis of the distortions of the striped pattern, it is possible to reconstruct the 3D structure of the skin precisely in an objective and reproducible manner.[12, 13]
The PRIMOS System, a phaseshift rapid in vivo measurement of the skin consists of a digital micro-mirror device (DMD) as a projection unit and a charge-coupled device (CCD) camera used as a recording unit (1,000 by 620 pixels). The DMD consists of an array of 1,024 by 768 16-μm² mirrors. Each mirror covers one cell of a complementary metal oxide semiconductor static random access memory. Depending on the data in the underlying memory cell, each mirror can be tilted, by means of electrostatic forces, +10° (ON) or −10° (OFF). In the ON position, light is reflected through a projection lens on the surface, whereas mirrors set to the OFF position reflect the light to an absorber. This technique allows projection of a high-resolution pattern of parallel stripes on the skin surface that the CCD camera records. The PRIMOSpremium device used in this study offers a field of view of 24 by 14 by 13 mm and measures wrinkle properties with a precision of 40 to 50 μm.
Three-dimensional measurements were taken of the crow's feet (45°), forehead (0°) and glabella lines (0°) in a standardized position. Macrocurvature of the skin was filtered using the robust high-pass filter; the glabellar area was also filtered for hairs that could disturb the analyses. Three-dimensional surface profiles were evaluated using the special wrinkle algorithm offered by PRIMOS software 5.6.
Following the recommendation of the Guideline for Evaluation of Anti-Wrinkle Products, five parameters were used to analyze the data (Table 2). Wd is the overall average wrinkle depth, maxWd is the average depth of the wrinkle with the largest volume, and lWd describes the maximum wrinkle depth (all in μm). Total wrinkle volume (Wv) is taken as the sum of the volumes of the individual wrinkles in the measurement field (mm³). Wa (%) represents the percentage of the measurement field area that the wrinkles occupy.
|Overall average wrinkle depth (Wd)||μm|
|Average maximum wrinkle depth (maxWd)||μm|
|Maximum largest wrinkle depth (IWd)||μm|
|Total wrinkle volume (Wv)||mm³|
|Percentage wrinkle area (Wa)||%|
Validated Assessment Scales
Crow's feet and forehead and glabellar lines were assessed using standardized photographs. Subjects were photographed (mediscope, FotoFinder Systems GmbH, Bad Birnbach) at an angle of 0° and at an angle of 45° from both sides. In all cases, the face was depicted at rest, without mimic expression. Subsequently, the pictures were digitally cropped to the pattern of the photonumeric VAS for crow's feet, and forehead and glabellar lines.[16-18] These grading scales currently represent one of the most precise, standardized, and validated rating scales for facial rhytides and are well established in aesthetic medicine.[18, 19] Two trained investigators evaluated all images. Each investigator was provided with an identical set of 600 randomized photographs displaying periorbital, glabellar, and forehead lines. The grades of the rating scales are 0 for no wrinkles, 1 for very fine wrinkles, 2 for fine wrinkles, 3 for moderate wrinkles, and 4 for severe wrinkles.
SPSS Statistics 20 (IBM, Armonk, NY) was used for all statistical analyses. Conformity with Gaussian distribution was determined using the Kolmogorov-Smirnov test. The nonparametric Mann-Whitney test was used to identify significant differences between the youngest and oldest age groups, as well as between two consecutive age groups. In addition, Kendall tau-b (τb) rank correlation coefficient was used to determine interrater reliability between the two investigators. Values of Tb range from −1 (100% negative association) to 1 (100% positive association). A correlation coefficient of τb >0.7 indicates a high statistical relationship, whereas a coefficient between 0.4 and 0.7 represents a moderate one. A correlation coefficient of τb <0.4 indicates low relationship. p < .05 was considered to be statistically significant.
The minimal measuring accuracy of the 3D fringe projection method is approximately 40 to 50 μm because of pulse beat and other micro-movements in vivo. Therefore, values of <50 μm were replaced using a corresponding default value to avoid bias due to measuring errors, although measurement accuracy is not compromised because an average wrinkle depth of 60 to 100 μm is required for visualization by the human eye.
All data from the 200 subjects were used for statistical analysis. Demographic data is shown in Table 3.
|Mean ± Standard Deviation (Range)|
|Total||45.06 ± 14.94 (22–69)||44.80 ± 14.90 (21–70)|
|20–29||25.36 ± 2.16||25.70 ± 2.48|
|30–39||32.25 ± 1.71||33.23 ± 2.90|
|40–49||44.57 ± 3.31||44.23 ± 3.09|
|50–59||55.85 ± 1.99||54.20 ± 3.13|
|60–70||63.30 ± 2.98||66.63 ± 2.61|
Validated Assessment Scales
Inter-rater reliability (periorbital lines, τb = 0.802, p < .001; glabellar lines, τb = 0.760, p < .001; forehead lines, τb = 0.800, p < .001) was calculated based on 200 cases rated by two investigators. Thus, agreement between the experts was considerable.
Mean VAS values for crow's feet and glabellar and forehead lines are shown in Figure 1. Results of men and women indicate a significant increase in wrinkle severity at all locations from the youngest[20-29] to the eldest age group (60–70). Wrinkles clinically manifest in men earlier and are more severe than in women. Very fine wrinkles on the forehead are visible in men in the youngest age group,[20-29] whereas forehead lines in women are first evident between 40 and 49. Of the three sites evaluated, crow's feet were the first wrinkles visible in women. On average, clinical manifestation begins in the fourth decade of life. Furthermore, crow's feet are the most marked in the eldest age group. Glabellar lines are not visible in either sex before the age of 40 but increase significantly (p < .05) within 1 decade. Glabellar wrinkle severity increased by a factor of 4.9 from age group II to V in women, whereas the results of men increase by a factor of 2 for the same time period. All assessed locations differed significantly from each other, with the exception of forehead and periorbital lines in women.
In both sexes and all age groups, up to five individual cases were found with wrinkle characteristics that deviate considerably from the mean. This deviation can be limited to single locations with exceptionally high or low wrinkle severity or relate to the overall wrinkle severity.
Three-Dimensional Fringe Projection Method
Skin topography was further biophysically assessed using the 3D fringe projection method. The parameters Wd, maxWd, lWd, Wv, and Wa were statistically analyzed for wrinkle evaluation (Table 4).
|Periorbital Lines||Glabellar Lines||Forehead Lines||Periorbital Lines||Glabellar Lines||Forehead Lines|
|Mean ± standard deviation|
|Wd, μm||20–29||50.27 ± 4.21||54.00 ± 15.77||48.18 ± 18.14||59.03 ± 13.92||79.00 ± 57.51||58.67 ± 16.43|
|30–39||68.38 ± 38.83||53.13 ± 17.32||43.63 ± 5.04||76.93 ± 37.90||108.17 ± 71.59||79.27 ± 38.40|
|40–49||75.71 ± 27.03||99.86 ± 32.47||67.71 ± 34.37||104.34 ± 44.28||156.45 ± 82.21||118.69 ± 56.67|
|50–59||80.31 ± 30.17||185.00 ± 91.46||85.15 ± 40.80||120.17 ± 45.31||231.45 ± 93.31||135.00 ± 48.84|
|60–70||106.60 ± 57.69||207.30 ± 97.82||71.70 ± 33.17||158.03 ± 54.87||283.57 ± 69.11||182.63 ± 87.76|
|maxWd, μm||20–29||49.36 ± 4.22||54.27 ± 16.04||48.91 ± 20.81||59.03 ± 14.91||79.77 ± 58.31||60.10 ± 18.19|
|30–39||70.88 ± 44.69||53.13 ± 17.32||43.63 ± 5.04||80.10 ± 45.21||111.03 ± 76.86||82.83 ± 43.97|
|40–49||78.57 ± 31.89||112.57 ± 39.69||68.14 ± 34.86||110.00 ± 55.32||161.17 ± 86.01||122.28 ± 58.71|
|50–59||84.23 ± 36.54||193.62 ± 86.23||94.62 ± 51.49||125.07 ± 52.55||244.38 ± 102.88||143.52 ± 56.68|
|60–70||117.20 ± 76.32||212.70 ± 102.16||72.40 ± 33.62||168.23 ± 64.07||300.13 ± 78.55||203.33 ± 108.20|
|lWd, μm||20–29||101.82 ± 12.66||119.55 ± 32.61||127.45 ± 74.18||137.77 ± 51.33||191.50 ± 174.72||165.47 ± 66.02|
|30–39||154.13 ± 103.22||118.50 ± 43.84||106.50 ± 15.96||176.07 ± 106.45||271.97 ± 225.55||233.73 ± 151.10|
|40–49||170.86 ± 83.88||304.43 ± 117.15||195.14 ± 123.88||285.00 ± 186.95||396.66 ± 220.72||333.83 ± 166.65|
|50–59||231.23 ± 149.43||537.38 ± 235.34||239.23 ± 125.07||311.79 ± 136.92||628.79 ± 364.44||378.79 ± 148.63|
|60–70||277.30 ± 189.79||570.90 ± 318.02||198.80 ± 103.05||419.60 ± 172.72||791.90 ± 482.39||539.40 ± 267.81|
|Wv, mm³||20–29||0.30 ± 0.15||0.61 ± 0.50||1.51 ± 2.60||0.85 ± 0.87||1.76 ± 3.80||2.15 ± 1.76|
|30–39||0.88 ± 1.09||0.38 ± 0.15||0.81 ± 0.52||1.69 ± 2.25||3.57 ± 4.80||4.62 ± 5.14|
|40–49||1.32 ± 1.45||5.63 ± 3.51||4.37 ± 4.59||5.00 ± 4.84||8.19 ± 7.23||8.94 ± 7.99|
|50–59||2.86 ± 2.77||10.93 ± 7.20||6.66 ± 6.57||7.028 ± 6.41||12.41 ± 8.48||12.51 ± 7.18|
|60–70||4.01 ± 5.86||13.70 ± 11.75||4.40 ± 3.71||12.63 ± 8.27||15.09 ± 7.59||18.53 ± 12.90|
|Wa,%||20–29||0.01 ± 0.04||0.69 ± 0.69||1.98 ± 1.83||0.92 ± 0.92||0.91 ± 1.16||3.68 ± 2.73|
|30–39||0.72 ± 0.53||0.33 ± 0.11||1.65 ± 0.92||1.30 ± 1.24||1.69 ± 1.84||4.98 ± 3.55|
|40–49||1.13 ± 0.99||4.04 ± 2.41||4.82 ± 3.93||3.16 ± 2.40||3.19 ± 2.41||6.81 ± 3.93|
|50–59||2.25 ± 0.77||4.54 ± 1.17||6.01 ± 4.45||3.82 ± 2.60||3.87 ± 1.85||9.08 ± 3.52|
|60–70||2.09 ± 1.83||4.48 ± 2.11||4.97 ± 3.07||5.69 ± 2.78||4.04 ± 1.46||10.07 ± 3.72|
Wrinkle depth (Wd, maxWd, lWd), wrinkle volume (Wv), and wrinkle area (Wa) increase progressively with age in both sexes (Figure 2). The results of all wrinkle parameters in men are significantly (p < .05) higher than the results of the female subjects of a similar age. In the youngest age group of both sexes, the glabellar fold is the location with the highest values. This location also shows the greatest increase with aging. Glabellar wrinkle depth (Wd) increased in women from 54 μm in the youngest to 207.3 μm in the oldest age group. In men, it increase from 79 μm to 283.6 μm from the youngest to the oldest age group. The glabella is the location with the greatest wrinkle depth (Wd) and the greatest wrinkle volume (Wv) in the oldest age group in both sexes. For both sexes, total wrinkle area (Wa) is largest at the forehead. The ratio increases from 3.68% (AG I) to 10.07% (AG V) in men and from 1.98% (AG I) to 4.97% (AG V) in women. Overall, forehead lines of women and crow's feet of men have less-pronounced wrinkle properties than the other locations.
Although the increase in wrinkle severity with age was linear at all locations in men, the wrinkle depth of glabellar and forehead lines in woman was small until the age of 40 and increased distinctly in the fifth decade of life. A significant (p < .005) increase in glabellar wrinkle depth parameters can be found between age 40 to 49 and 50 to 59 in women.
The topography of the skin changes with age and eventually results in the development of facial wrinkles, the most visible morphologil change associated with the aging process of human skin. Whereas molecular mechanisms of skin aging are well understood, little information is available concerning the clinical onset and lifetime development of wrinkles in the human face. With 200 subjects, we performed the first systematic evaluation of age-related wrinkle development in men and women using 3D measurements and VAS.
Wrinkles and Aging
The first manifestation of facial wrinkles occurs on the forehead and the last in the glabellar area. Whereas crow's feet constantly increase approximately 0.5 VAS grades every 10 years, wrinkle severity of glabellar lines increases slowly until the age of 40 and increases sharply in the fifth decade of life (Figure 3). An underlying explanation for these local variations in wrinkle development remains unclear, but one can hypothesize that the more frequently a location is used, the more consistently wrinkle severity increases throughout one's lifetime. The periorbital muscle and eyelid are essential for emotional response and functionality. Squinting of the eyes to protect against sunlight or to optimize visual function are physiologic muscle movements, which can cause hyperkinetic periorbital lines, known as crow's feet. Crow's feet also occur through mimic expression. Thus, it is conceivable that the constant increase in wrinkle severity in crow's feet is caused by frequent mimic and physiologic movements. In contrast, the forehead and glabellar areas are mainly used to express emotion, such as joy or anger, and therefore may be less frequently used than the periorbital region. This, together with the thicker skin at the glabella and forehead areas, could be a reason for the differences in the wrinkle development between the areas.
Wrinkle severity considerably deviates in individual cases from the mean value independent of age and location, probably influenced by individual mimic expression. The more frequently a muscle is used during one's lifetime, the higher the wrinkle severity at the skin surface even without gesture and mimic. Therefore, wrinkle severity in people aged 20 to 50 varies between no wrinkles (VAS grade 0) and moderate wrinkles (VAS grade 3), whereas the variations in older subjects are between very fine and fine wrinkles (VAS grades 1 and 2) to severe wrinkles (VAS grade 4). The fact that none of the 50- to 70-year-old men and women had no wrinkles (VAS grade 0) reveals that, by the age of 50, humans usually have visible facial wrinkles at the forehead and glabella and crow's feet. At older ages, the cumulative lifetime exposure of the skin to UV radiation and other extrinsic factors may increase wrinkle severity.[23-26]
Evaluation of 3D fringe projection methods shows that wrinkle depth (Wd) at glabellar frown lines increases the most during one's lifetime. The assessed wrinkle depth of the glabellar lines in the eldest age group was more than 100 μm deeper than of the forehead or periorbital lines. During one's lifetime, wrinkles simultaneously increase in depth, width, and volume. These findings are congruent with the study results of Akazaki and colleagues, who reported an increasing ratio between wrinkle depth and width with chronologic aging assessed using the fringe projection method. A reduction in wrinkle depth and volume can also be seen after treatment with incobotulinumtoxinA (unpublished data). With decreasing efficacy of chemodenervation, Wd and Wv increase simultaneously.
In summary, the clinical appearance of wrinkles on the face increases chronologically with age (Figure 3). On average, wrinkles first manifest at the forehead then at the periorbital region, or so-called crow's feet, followed by wrinkles at the glabellar area. By the age of 50, men and women usually have wrinkles in all three areas, although large deviations between locations, even in similar age groups, are observed, most likely due to the individual mimic expressions.
Our study data show sex-specific differences in the lifetime development of facial wrinkles. Generally, wrinkle severity increases with age in both sexes, but the development of wrinkles starts at an earlier age and is significantly more marked in men, especially at the forehead. These findings are contrary to the common opinion that wrinkles appear later in men and are less severe, although other studies evaluating sex differences in skin aging are rare, and results are inconsistent. In contrast to our results, Paes and colleagues found significantly more and deeper wrinkles in the perioral region of women, whereas Akiba and colleagues demonstrated more wrinkles and greater wrinkle severity at the upper face of men. The difference in number of wrinkles between men and women may largely reflect the difference in sun exposure. One cannot necessarily assume that men are exposed to more UV radiation than women, but study results indicate that women tend to be more-frequent sunscreen users than men.[30, 31] Therefore, it is possible that greater exposure to extrinsic factors, particularly UV radiation, may cause the higher lifetime development of wrinkles in men and is less likely a result of intrinsic sex differences. Further research is needed to identify the reasons for sex differences in wrinkle onset and development.
The influence of menopause on skin wrinkling in women has been discussed in previous studies.[32-36] In this study, we ensured, by personal interviews, that women in age groups IV and V were postmenopausal and without hormonal replacement therapy, whereas younger women still had menstrual cycles. The direct comparison of peri- (aged 40–49) and postmenopausal women (aged 50–59) in our study indicates a significantly greater severity of glabellar wrinkles in the postmenopausal group, although the greatest increase in overall wrinkle severity is found in women in their fifth decade. The difference between individuals aged 30 to 39 and those aged 40 to 49 was greater than between any other continuous age groups, independent of sex. This finding supports the assumption of Hillebrand and colleagues and others that changes in hormonal status due to perimenopause might be more important for the acceleration of skin wrinkling in women than low hormonal status per se.
Regarding sex-specific differences, it can be concluded that facial wrinkles affect men significantly earlier and more strongly than women. The influence of menopause on skin surface changes cannot be finally clarified, although it can be assumed that being perimenopausal may accelerate the development of facial wrinkles.
VAS Versus Fringe Projection Method
The corresponding results of the fringe projection method and VAS indicate that both methods are particularly suitable to quantify wrinkle severity, although specific differences are noticeable. Although glabellar lines are the site with the highest severity when measured biophysically, they appear to be less marked in clinical ratings. The inverse result can be found for forehead lines, which are more marked in clinical ratings. Furthermore, with the fringe projection method, it was possible to measure fine wrinkles even in the youngest age group,[20-29] whereas clinical rating indicated no wrinkles in this group.
The results confirm that the 3D fringe projection method can be used to measure fine wrinkles that the human eye cannot recognize. Moreover, biophysical measurement is free of any bias that may influence even well-trained evaluators. On the other hand, clinical rating by trained investigators captures the overall impression of the area examined, including skin color and further anatomic changes, rather than simply assessing a particular wrinkle parameter. Therefore, clinical assessment by trained investigators using validated scales may have more clinical relevance.
One limitation of this study is the unequal distribution of sex, which is probably associated with less statistical sensitivity in women. As a consequence thereof, differences that have been shown to be statistically significant in men may not be significant in women. Also of importance is the technical limitation of the 3D fringe projection device used in this study to assess wrinkles smaller than 50 μm. This could have resulted in less-precise assessment of very fine wrinkles, although statistical evaluation showed the validity and reliability of the results.
Based on the statistical analysis of the data of 200 men and women, the present study verifies the progressive increase in crow's feet and forehead and glabellar lines during one's lifetime. The strongest increase in wrinkle severity is found in the fifth decade of life. At this point, age wrinkles become not only deeper, but also wider, resulting in a higher volume and therefore in greater clinical visibility. By the age of 50, crow's feet and forehead and glabellar wrinkles affect men and women. Men develop wrinkles earlier and more prominently than women, especially forehead lines, which are already marked in men in their 20s.
Being perimenopausal may cause accelerated development of facial wrinkles, although the effect of menopause on skin wrinkling cannot be definitively clarified. A further study assessing wrinkle severity and hormonal status should be conducted to better understand the hormonal influence on wrinkle development.
The study showed that the 3D fringe projection method and VAS are suitable to evaluate the lifetime development of facial wrinkles, although biophysical measuring is particularly useful to indicate even the earliest changes in skin topography, whereas visual assessment by trained investigators might be of greater importance for practical clinical relevance.
The results obtained in this systematic study provide detailed insight into the progression of facial wrinkle development in men and women. The findings will be helpful for future studies that evaluate the influence of procedures and treatments in aesthetic dermatology, including dermal fillers, botulinum toxins, and laser and radiofrequency treatments. More importantly, the data will help to understand wrinkles as part of the natural human aging process that should always be treated with deliberation to preserve a natural appearance.
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- 15Task Force Committee for Evaluation of Anti-Aging Function. Guidelines for evaluation of anti-wrinkle products. J Jpn Cosmet Sci Soc 2007;31:423–31.
- 24Quantitative evaluation of skin condition in an epidemiological survey of females living in northern versus southern Japan. J Dermatol Sci 2001;27:S42–52., , , , et al.
- 29Influence of chronic UV exposure and lifestyle on facial skin photo-aging—results from a pilot study. J Epidemiol 1999;9:136–42., , , , et al.
- 37Does hormone therapy improve age-related skin changes in postmenopausal women? A randomized, double-blind, double-dummy, placebo-controlled multicenter study assessing the effects of norethindrone acetate and ethinyl estradiol in the improvement of mild to moderate age-related skin changes in postmenopausal women. J Am Acad Dermatol 2008;59:397–404., , .